Stilbene derivatives, light-emitting element and light-emitting device

ABSTRACT

The present invention provides a novel substance having an excellent color purity of blue, a light-emitting element and a light-emitting device using the novel substance. A stilbene derivative has a structure shown by the general formula (1). In the general formula (1), R 1  is hydrogen, an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbon atoms. R 2  is an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 25 carbon atoms. Each of R 3  to R 5  is hydrogen or an alkyl group having 1 to 4 carbon atoms. Ar 1  is an aryl group having 6 to 25 carbon atoms.

This application is a continuation of U.S. application Ser. No.12/351,138, filed on Jan. 9, 2009 now U.S. Pat. No. 7,898,171 which is adivisional of U.S. application Ser. No. 11/542,157, filed on Oct. 2,2006 (now U.S. Pat. No. 7,476,745 issued Jan. 13, 2009) which claimspriority of foreign application serial nos. 2005-292366 filed on Oct. 5,2005 in Japan and 2005-343674 filed on Nov. 29, 2005 in Japan under 35U.S.C. 119.

TECHNICAL FIELD

The present invention relates to stilbene derivatives, light-emittingelements with the use of stilbene derivatives and light-emitting deviceshaving the light-emitting elements.

BACKGROUND ART

A light-emitting element having features such as thinness, lightweight,and rapid response is expected to be applied to flat panel displays ofthe next generation. In addition, it is said that a light-emittingdevice in which light-emitting elements are arranged in matrix issuperior to conventional liquid crystal display devices in viewing angleand visibility.

A light-emitting element is formed by interposing a layer including aluminescent substance between a pair of electrodes (an anode and acathode), and it is said that emission mechanism thereof is as follows:when a voltage is applied between both electrodes, holes injected fromthe anode and electrons injected from the cathode are recombined in alight-emitting layer in the layer including a luminescent substance,thereby forming a molecular exciton by recombination in an emissioncenter, and energy is released to emit light when the molecular excitonreturns to a ground state. By such a mechanism, such a light-emittingelement is referred to as a current excitation type light-emittingelement. A singlet excitation state and a triplet excitation state canbe given as types of an excitation state formed by a luminescentsubstance. Light emission from a singlet excitation state is referred toas fluorescence and light emission from a triplet excitation state isreferred to as phosphorescence.

Emission wavelength of a light-emitting element is determined by energydifference between a ground state and an excited state, that is, a bandgap, of a light-emitting molecule included in the light-emittingelement. Therefore, various emission colors can be obtained by devisinga structure of the light-emitting molecule. By manufacturing alight-emitting device using light-emitting elements capable of emittingred light, blue light, and green light, which are the three primarycolors of light, a full-color light-emitting device can be manufactured.

However, until now, there has been a problem in that it is difficult torealize a light-emitting element having high reliability and excellentcolor purity. As a result of recent development of materials, highreliability and excellent color purity of light-emitting elements forgreen and red have been achieved. However, in particular, highreliability and excellent color purity of a light-emitting element forblue has not been realized, and many researches have been done (forexample, Reference 1: Japanese Published Patent Application No.2004-75580).

DISCLOSURE OF THE INVENTION

The present invention has been made in view of the above describedproblems. It is an object of the present invention to provide a novelsubstance which provides excellent color purity of blue, alight-emitting element and a light-emitting device using the novelsubstance.

A structure of the present invention is to provide novel stilbenederivatives. A stilbene derivative of the present invention includes astructure shown in the following general formula (1).

In the general formula (1), R¹ is hydrogen, an alkyl group having 1 to 4carbon atoms, or an aryl group having 6 to 25 carbon atoms, and the arylgroup may have an alkyl group having 1 to 4 carbon atoms. In addition,R² is an alkyl group having 1 to 4 carbon atoms or an aryl group having6 to 25 carbon atoms, and the aryl group may have an alkyl group having1 to 4 carbon atoms. Each of R³ to R⁵ is hydrogen or an alkyl grouphaving 1 to 4 carbon atoms. Further, Ar¹ is an aryl group having 6 to 25carbon atoms, and the aryl group may have an alkyl group having 1 to 4carbon atoms.

Also, a stilbene derivative of the present invention includes astructure represented by the following general formula (2).

In the general formula (2), R¹ is hydrogen, an alkyl group having 1 to 4carbon atoms, or an aryl group having 6 to 25 carbon atoms, and the arylgroup may have an alkyl group having 1 to 4 carbon atoms. R² is an alkylgroup having 1 to 4 carbon atoms or an aryl group having 6 to 25 carbonatoms, and the aryl group may have an alkyl group having 1 to 4 carbonatoms. Each of R³ to R⁵ is hydrogen or an alkyl group having 1 to 4carbon atoms. Further, each of R⁶ to R¹⁰ is hydrogen, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms, and the aryl group may have an alkyl group having 1 to 4 carbonatoms.

Also, a stilbene derivative of the present invention includes astructure represented by the following general formula (3).

In the general formula (3), R¹ is hydrogen, an alkyl group having 1 to 4carbon atoms, or an aryl group having 6 to 25 carbon atoms, and the arylgroup may have an alkyl group having 1 to 4 carbon atoms. R² is an alkylgroup having 1 to 4 carbon atoms or an aryl group having 6 to 25 carbonatoms, and the aryl group may have an alkyl group having 1 to 4 carbonatoms. Ar¹ is an aryl group having 6 to 25 carbon atoms, and the arylgroup may have an alkyl group having 1 to 4 carbon atoms.

In addition, a stilbene derivative of the present invention includes astructure represented by the following general formula (4).

In the general formula (4), R¹ is hydrogen, an alkyl group having 1 to 4carbon atoms, or an aryl group having 6 to 25 carbon atoms, and the arylgroup may have an alkyl group having 1 to 4 carbon atoms. In addition,R² is an alkyl group having 1 to 4 carbon atoms or an aryl group having6 to 25 carbon atoms; and the aryl group may have an alkyl group having1 to 4 carbon atoms. In addition, each of R⁶ to R¹⁰ is hydrogen, analkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 25carbon atoms, and the aryl group may have an alkyl group having 1 to 4carbon atoms.

Further, a stilbene derivative of the present invention includes astructure represented by the following general formula (5).

In the general formula (5), each of R¹ and R² is hydrogen, an alkylgroup having 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms, and the aryl group may have an alkyl group having 1 to 4 carbonatoms. In addition, each of R³ to R⁵ is hydrogen or an alkyl grouphaving 1 to 4 carbon atoms. Ar¹ is an aryl group having 6 to 25 carbonatoms, and the aryl group may have an alkyl group having 1 to 4 carbonatoms.

Also, a stilbene derivative of the present invention includes astructure represented by the following general formula (6).

In the general formula (6), each of R¹ and R² is hydrogen, an alkylgroup having 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms, and the aryl group may have an alkyl group having 1 to 4 carbonatoms. In addition, each of R³ to R⁵ is hydrogen or an alkyl grouphaving 1 to 4 carbon atoms, each of R⁶ to R¹⁰ is hydrogen, an alkylgroup having 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms, and the aryl group may have an alkyl group having 1 to 4 carbonatoms.

Also, a stilbene derivative of the present invention includes astructure represented by the following general formula (7).

In the general formula (7), each of R¹ and R² is hydrogen, an alkylgroup having 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms, and the aryl group may have an alkyl group having 1 to 4 carbonatoms. In addition, Ar¹ is an aryl group having 6 to 25 carbon atoms,and the aryl group may have an alkyl group having 1 to 4 carbon atoms.

Moreover, a stilbene derivative of the present invention includes astructure represented by the following general formula (8).

In the general formula (8), each of R¹ and R² is hydrogen, an alkylgroup having 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms, and the aryl group may have an alkyl group having 1 to 4 carbonatoms. In addition, each of R⁶ to R¹⁰ is hydrogen, an alkyl group having1 to 4 carbon atoms, or an aryl group having 6 to 25 carbon atoms, andthe aryl group may have an alkyl group having 1 to 4 carbon atoms.

The present invention includes a structure of a light-emitting elementwhich has a light-emitting layer including a stilbene derivative asdescribed above. One feature of a stilbene derivative in accordance withthe present invention is to emit blue light with high color purity, andthus, it is mainly used as a guest material and forms a light-emittinglayer together with another host material.

In the above structure, fine control of emission color for a stilbenederivative of the present invention is possible, depending on a polarityof a host material, and thus, a desired emission color can be obtainedby appropriately selecting a host material.

Furthermore, the present invention includes a structure of alight-emitting device which has a light-emitting element having alight-emitting layer including a stilbene derivative as described above.

By implementing the present invention, blue emission with excellentcolor purity is obtained and a stilbene derivative with excellentluminous efficiency can be provided. In addition, by manufacturing alight-emitting element using a stilbene derivative as described above, ablue light-emitting element with excellent color purity and alight-emitting device using it can be provided. Moreover, alight-emitting element and a light-emitting device having excellentluminous efficiency can be provided. A light-emitting element and alight-emitting device having a longer lifetime can be provided.

BRIEF DESCRIPTION OF DRAWINGS

In the accompanying drawings:

FIG. 1 shows a light-emitting element according to an aspect of thepresent invention;

FIG. 2 shows, a light-emitting element according to an aspect of thepresent invention;

FIGS. 3A and 3B show light-emitting elements according to an aspect ofthe present invention;

FIGS. 4A and 4B show a light-emitting device according to an aspect ofthe present invention;

FIGS. 5A to 5E show electronic devices according to an aspect of thepresent invention;

FIGS. 6A and 6B are ¹NMR charts of PCA;

FIG. 7 is a ¹NMR chart of PCAS according to an aspect of the presentinvention;

FIG. 8 shows an absorption spectrum of PCAS according to an aspect ofthe present invention;

FIG. 9 shows an emission spectrum of PCAS according to an aspect of thepresent invention;

FIG. 10 is a ¹NMR Chart of PCATBS according to an aspect of the presentinvention;

FIG. 11 shows an absorption spectrum of PCATBS according to an aspect ofthe present invention;

FIG. 12 shows an emission spectrum of PCATBS according to an aspect ofthe present invention;

FIG. 13 is a ¹NMR chart of PCA2S according to an aspect of the presentinvention;

FIG. 14 shows an absorption spectrum of PCA2S according to an aspect ofthe present invention;

FIG. 15 shows an emission spectrum of PCA2S according to an aspect ofthe present invention;

FIGS. 16A and 16B are ¹MNR charts of YGA;

FIG. 17 is a ¹NMR chart of YGAS according to an aspect of the presentinvention;

FIG. 18 shows an absorption spectrum of YGAS according to an aspect ofthe present invention;

FIG. 19 shows an emission spectrum of YGAS according to an aspect of thepresent invention;

FIG. 20 is a ¹NMR chart of YGA2S according to an aspect of the presentinvention;

FIG. 21 shows an absorption spectrum of YGA2S according to an, aspect ofthe present invention;

FIG. 22 shows an emission spectrum of YGA2S according to an aspect ofthe present invention;

FIG. 23 shows element characteristics of a light-emitting elementmanufactured using PCAS;

FIG. 24 shows element characteristics of a light-emitting elementmanufactured using PCAS;

FIG. 25 shows element characteristics of a light-emitting elementmanufactured using PCAS;

FIG. 26 shows element characteristics of a light-emitting elementmanufactured using PCAS;

FIG. 27 shows element characteristics of a light-emitting elementmanufactured using PCATBS;

FIG. 28 shows element characteristics of a light-emitting elementmanufactured using PCATBS;

FIG. 29 shows element characteristics of a light-emitting elementmanufactured using PCATBS;

FIG. 30 shows element characteristics of a light-emitting elementmanufactured using PCATBS;

FIG. 31 shows element characteristics of a light-emitting elementmanufactured using PCA2S;

FIG. 32 shows element characteristics of a light-emitting elementmanufactured using PCA2S;

FIG. 33 shows element characteristics of a light-emitting elementmanufactured using PCA2S;

FIG. 34 shows element characteristics of a light-emitting elementmanufactured using PCA2S;

FIG. 35 shows element characteristics of a light-emitting elementmanufactured using YGAS;

FIG. 36 shows element characteristics of a light-emitting elementmanufactured using YGAS;

FIG. 37 shows element characteristics of a light-emitting elementmanufactured using YGAS;

FIG. 38 shows element characteristics of a light-emitting elementmanufactured using YGAS;

FIG. 39 shows element characteristics of a light-emitting elementmanufactured using YGA2S;

FIG. 40 shows element characteristics of a light-emitting elementmanufactured using YGA2S;

FIG. 41 shows element characteristics of a light-emitting elementmanufactured using YGA2S;

FIG. 42 shows element characteristics of a light-emitting elementmanufactured using YGA2S;

FIG. 43 shows element characteristics of a light-emitting elementmanufactured using YGA2S;

FIG. 44 shows element characteristics of a light-emitting elementmanufactured using YGA2S;

FIG. 45 shows element characteristics of a light-emitting elementmanufactured using YGA2S;

FIG. 46 shows element characteristics of a light-emitting elementmanufactured using YGA2S;

FIG. 47 shows element characteristics of a light-emitting elementmanufactured using YGA2S;

FIG. 48 shows element characteristics of a light-emitting elementmanufactured using YGA2S;

FIG. 49 shows element characteristics of a light-emitting elementmanufactured using YGA2S;

FIG. 50 shows element characteristics of a light-emitting elementmanufactured using YGA2S;

FIG. 51 shows a result of a reliability test of a light-emitting elementmanufactured using YGA2S;

FIGS. 52A and 52B are ¹NMR charts of PCA; and

FIGS. 53A and 53B are ¹NMR charts of PCA.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the embodiment modes of the present invention will bedescribed with reference to the accompanying drawings. The presentinvention can be carried out in many different modes. It is easilyunderstood by those skilled in the art that modes and details hereindisclosed can be modified in various ways without departing from thespirit and the scope of the present invention. It should be noted thatthe present invention should not be interpreted as being limited to thedescription of the embodiment modes to be given below.

Embodiment Mode 1

Stilbene derivatives of the present invention include structuresrepresented by the following general formulas (1) to (8).

In the formula, R¹ is hydrogen, an alkyl group having 1 to 4 carbonatoms or an aryl group having 6 to 25 carbon atoms. As the alkyl grouphaving 1 to 4 carbon atoms, a methyl group, an ethyl group, an n-propylgroup, an isopropyl group, an n-butyl group, an isobutyl group, ans-butyl group, a t-butyl group and the like are given. As the aryl grouphaving 6 to 25 carbon atoms, a phenyl group, a naphthyl group, abiphenylyl group, a fluorenyl group and the like are given. Thedescribed aryl group may have a substituent or may not. When such anaryl group has a substituent, the substituent of the aryl group ispreferably an alkyl group having 1 to 4 carbon atoms, specifically, amethyl group, an ethyl group, an n-propyl group, an isopropyl group, ann-butyl group, an isobutyl group, an s-butyl group, a t-butyl group andthe like can be given. Among them, the methyl group or the t-butyl groupis preferable. In addition, as the fluorenyl group,9,9-dimethylfluoren-2-yl, or spiro-9,9′-bifluoren-2-yl is preferable.

In the formula, R² is an alkyl group having 1 to 4 carbon atoms or anaryl group having 6 to 25 carbon atoms. As the alkyl group having 1 to 4carbon atoms, a methyl group, an ethyl group, an n-propyl group, anisopropyl group, an n-butyl group, an isobutyl group, an s-butyl group,a t-butyl group and the like are given. As the aryl group having 6 to 25carbon atoms, a phenyl group, a naphthyl group, a biphenylyl group, afluorenyl group and the like are given. The aryl group may have asubstituent or may not. When such an aryl group has a substituent, thesubstituent of the aryl group is preferably an alkyl group having 1 to 4carbon atoms, specifically, a methyl group, an ethyl group, an n-propylgroup, an isopropyl group, an n-butyl group, an isobutyl group, ans-butyl group, a t-butyl group and the like can be given. Among them,the methyl group or the t-butyl group is preferable. In addition, as thefluorenyl group, 9,9-dimethylfluoren-2-yl, or spiro-9,9′-bifluoren-2-ylis preferable.

In the formula, each of R³ to R⁵ is hydrogen or an alkyl group having 1to 4 carbon atoms. As the alkyl group having 1 to 4 carbon atoms, amethyl group, an ethyl group, an n-propyl group, an isopropyl group, ann-butyl group, an isobutyl group, an s-butyl group, a t-butyl group andthe like are given.

Ar¹ is an aryl group having 6 to 25 carbon atoms. As the aryl grouphaving 6 to 25 carbon atoms, a phenyl group, a naphthyl group, abiphenylyl group, a fluorenyl group and the like are given. The arylgroup may have a substituent or may not. When such an aryl group has asubstituent, the substituent of the aryl group is preferably an alkylgroup having 1 to 4 carbon atoms, specifically, a methyl group, an ethylgroup, an n-propyl group, an isopropyl group, an n-butyl group, anisobutyl group, an s-butyl group, a t-butyl group and the like can begiven. Among them, the methyl group or the t-butyl group is preferable.In addition, as the fluorenyl group, 9,9-dimethylfluoren-2-yl, orspiro-9,9′-bifluoren-2-yl is preferable.

In the formula, R¹ is hydrogen, an alkyl group having 1 to 4 carbonatoms or an aryl group having 6 to 25 carbon atoms. As the alkyl grouphaving 1 to 4 carbon atoms, a methyl group, an ethyl group, an n-propylgroup, an isopropyl group, an n-butyl group, an isobutyl group, ans-butyl group, a t-butyl group and the like are given. As the aryl grouphaving 6 to 25 carbon atoms, a phenyl group, a naphthyl group, abiphenylyl group, a fluorenyl group and the like are given. Thedescribed aryl group may have a substituent or may not. When such anaryl group has a substituent, the substituent of the -aryl group ispreferably an alkyl group having 1 to 4 carbon atoms, specifically, amethyl group, an ethyl group, an n-propyl group, an isopropyl group, ann-butyl group, an isobutyl group, an s-butyl group, a t-butyl group andthe like can be given. Among them, the methyl group or the t-butyl groupis preferable. In addition, as the fluorenyl group,9,9-dimethylfluoren-2-yl, or spiro-9,9′-bifluoren-2-yl is preferable.

In the formula, R² is an alkyl group having 1 to 4 carbon atoms or anaryl group having 6 to 25 carbon atoms. As the alkyl group having 1 to 4carbon atoms, a methyl group, an ethyl group, an n-propyl group, anisopropyl group, an n-butyl group, an isobutyl group, an s-butyl group,a t-butyl group and the like are given. As the aryl group having 6 to 25carbon atoms, a phenyl group, a naphthyl group, a biphenylyl group, afluorenyl group and the like are given. The aryl group may have asubstituent or may not. When such an aryl group has a substituent, thesubstituent of the aryl group is preferably an alkyl group having 1 to 4carbon atoms, specifically, a methyl group, an ethyl group, an n-propylgroup, an isopropyl group, an n-butyl group, an isobutyl group, ans-butyl group, a t-butyl group and the like can be given. Among them,the methyl group or the t-butyl group is preferable. In addition, as thefluorenyl group, 9,9-dimethylfluoren-2-yl, or spiro-9,9′-bifluoren-2-ylis preferable.

In the formula, each of R³ to R⁵ is hydrogen or an alkyl group havingcarbon atoms 1 to 4. As the alkyl group having 1 to 4 carbon atoms, amethyl group, an ethyl group, an n-propyl group, an isopropyl group, ann-butyl group, an isobutyl group, an s-butyl group, a t-butyl group andthe like are given.

In the formula, each of R⁶ to R¹⁰ is hydrogen, an alkyl group having 1to 4 carbon atoms, or an aryl group having 6 to 25 carbon atoms. As thealkyl group having 1 to 4 carbon atoms, a methyl group, an ethyl group,an n-propyl group, an isopropyl group, an n-butyl group, an isobutylgroup, an s-butyl group, a t-butyl group and the like are given. As thearyl group having 6 to 25 carbon atoms, a phenyl group, a naphthylgroup, a biphenylyl group, a fluorenyl group and the like are given. Thearyl group may have a substituent or may not. When such an aryl grouphas a substituent, the substituent of the aryl group is preferably analkyl group having 1 to 4 carbon atoms, specifically, a methyl group, anethyl group, an n-propyl group, an isopropyl group, an n-butyl group, anisobutyl group, an s-butyl group, a t-butyl group and the like can begiven. Among them, the methyl group or the t-butyl group is preferable.In addition, as the fluorenyl group, 9,9-dimethylfluoren-2-yl, orspiro-9,9′-bifluoren-2-yl is preferable.

In the formula, R¹ is hydrogen, an alkyl group having 1 to 4 carbonatoms or an aryl group having 6 to 25 carbon atoms. As the alkyl grouphaving 1 to 4 carbon atoms, a methyl group, an ethyl group, an n-propylgroup, an isopropyl group, an n-butyl group, an isobutyl group, ans-butyl group, a t-butyl group and the like are given. As the aryl grouphaving 6 to 25 carbon atoms, a phenyl group, a naphthyl group, abiphenylyl group, a fluorenyl group and the like are given. Thedescribed aryl group may have a substituent or may not. When such anaryl group has a substituent, the substituent of the aryl group ispreferably an alkyl group having 1 to 4 carbon atoms, specifically, amethyl group, an ethyl group, an n-propyl group, an isopropyl group, ann-butyl group, an isobutyl group, an s-butyl group, a t-butyl group andthe like can be given. Among them, the methyl group or the t-butyl groupis preferable. In addition, as the fluorenyl group,9,9-dimethylfluoren-2-yl, or spiro-9,9′-bifluoren-2-yl is preferable.

In the formula, R² is an alkyl group having 1 to 4 carbon atoms or anaryl group having 6 to 25 carbon atoms. As the alkyl group having 1 to 4carbon atoms, a methyl group, an ethyl group, an n-propyl group, anisopropyl group, an n-butyl group, an isobutyl group, an s-butyl group,a t-butyl group and the like are given. As the aryl group having 6 to 25carbon atoms, a phenyl group, a naphthyl group, a biphenylyl group, afluorenyl group and the like are given. The aryl group may have asubstituent or may not. When such an aryl group has a substituent, thesubstituent of the aryl group is preferably an alkyl group having 1 to 4carbon atoms, specifically, a methyl group, an ethyl group, an n-propylgroup, an isopropyl group, an n-butyl group, an isobutyl group, ans-butyl group, a t-butyl group and the like can be given. Among them,the methyl group or the t-butyl group is preferable. In addition, as thefluorenyl group, 9,9-dimethylfluoren-2-yl, or spiro-9,9′-bifluoren-2-ylis preferable.

In the formula, Ar¹ is an aryl group having 6 to 25 carbon atoms. As thearyl group having 6 to 25 carbon atoms, a phenyl group, a naphthylgroup, a biphenylyl group, a fluorenyl group and the like are given. Thearyl group may have a substituent or may not. When such an aryl grouphas a substituent, the substituent of the aryl group is preferably analkyl group having 1 to 4 carbon atoms, specifically, a methyl group, anethyl group, an n-propyl group, an isopropyl group, an n-butyl group, anisobutyl group, an s-butyl group, a t-butyl group and the like can begiven. Among them, the methyl group or the t-butyl group is preferable.In addition, as the fluorenyl group, 9,9-dimethylfluoren-2-yl, orspiro-9,9′-bifluoren-2-yl is preferable.

In the formula, R¹ is hydrogen, an alkyl group having 1 to 4 carbonatoms or an aryl group having 6 to 25 carbon atoms. As the alkyl grouphaving 1 to 4 carbon atoms, a methyl group, an ethyl group, an n-propylgroup, an isopropyl group, an n-butyl group, an isobutyl group, ans-butyl group, a t-butyl group and the like are given. As the aryl grouphaving 6 to 25 carbon atoms, a phenyl group, a naphthyl group, abiphenylyl group, a fluorenyl group and the like are given. Thedescribed aryl group may have a substituent or may not. When such anaryl group has a substituent, the substituent of the aryl group ispreferably an alkyl group having 1 to 4 carbon atoms, specifically, amethyl group, an ethyl group, an n-propyl group, an isopropyl group, ann-butyl group, an isobutyl group, an s-butyl group, a t-butyl group andthe like can be given. Among them, the methyl group or the t-butyl groupis preferable. In addition, as the fluorenyl group,9,9-dimethylfluoren-2-yl, or spiro-9,9′-bifluoren-2-yl is preferable.

In the formula, R² is an alkyl group having 1 to 4 carbon atoms or anaryl group having 6 to 25 carbon atoms. As the alkyl group having 1 to 4carbon atoms, a methyl group, an ethyl group, an n-propyl group, anisopropyl group, an n-butyl group, an isobutyl group, an s-butyl group,a t-butyl group and the like are given. As the aryl group having 6 to 25carbon atoms, a phenyl group, a naphthyl group, a biphenylyl group, afluorenyl group and the like are given. The aryl group may have asubstituent or may not. When such an aryl group has a substituent, thesubstituent of the aryl group is preferably an alkyl group having 1 to 4carbon atoms, specifically, a methyl group, an ethyl group, an n-propylgroup, an isopropyl group, an n-butyl group, an isobutyl group, ans-butyl group, a t-butyl group and the like can be given. Among them,the methyl group or the t-butyl group is preferable. In addition, as thefluorenyl group, 9,9-dimethylfluoren-2-yl, or spiro-9,9′-bifluoren-2-ylis preferable.

In the formula, each of R⁶ to R¹⁰ is hydrogen, an alkyl group having 1to 4 carbon atoms, or an aryl group having 6 to 25 carbon atoms. As thealkyl group having 1 to 4 carbon atoms, a methyl group, an ethyl group,an n-propyl group, an isopropyl group, an n-butyl group, an isobutylgroup, an s-butyl group, a t-butyl group and the like are given. As thearyl group having 6 to 25 carbon atoms, a phenyl group, a naphthylgroup, a biphenylyl group, a fluorenyl group and the like are given. Thearyl group may have a substituent or may not. When such an aryl grouphas a substituent, the substituent of the aryl group is preferably analkyl group having 1 to 4 carbon atoms, specifically, a methyl group, anethyl group, an n-propyl group, an isopropyl group, an n-butyl group, anisobutyl group, an s-butyl group, a t-butyl group and the like can begiven. Among them, the methyl group or the t-butyl group is preferable.In addition, as the fluorenyl group, 9,9-dimethylfluoren-2-yl, orspiro-9,9′-bifluoren-2-yl is preferable.

In the formula, each of R¹ and R² is hydrogen, an alkyl group having 1to 4 carbon atoms, or an aryl group having 6 to 25 carbon atoms. As thealkyl group having 1 to 4 carbon atoms, a methyl group, an ethyl group,an n-propyl group, an isopropyl group, an n-butyl group, an isobutylgroup, an s-butyl group, a t-butyl group and the like are given. As thearyl group having 6 to 25 carbon atoms, a phenyl group, a naphthylgroup, a biphenylyl group, a fluorenyl group and the like are given. Thearyl group may have a substituent or may not. When such an aryl grouphas a substituent, the substituent of the aryl group is preferably analkyl group having 1 to 4 carbon atoms, specifically, a methyl group, anethyl group, an n-propyl group, an isopropyl group, an n-butyl group, anisobutyl group, an s-butyl group, a t-butyl group and the like can begiven. Among them, the methyl group or the t-butyl group is preferable.In addition, as the fluorenyl group, 9,9-dimethylfluoren-2-yl, orspiro-9,9′-bifluoren-2-yl is preferable.

In the formula, each of R³ to R⁵ is hydrogen or an alkyl group having 1to 4 carbon atoms. As the alkyl group having 1 to 4 carbon atoms, amethyl group, an ethyl group, an n-propyl group, an isopropyl group, ann-butyl group, an isobutyl group, an s-butyl group, a t-butyl group andthe like are given.

In the formula, Ar¹ is an aryl group having 6 to 25 carbon atoms. As thearyl group having 6 to 25 carbon atoms, a phenyl group, a naphthylgroup, a biphenylyl group, a fluorenyl group and the like are given. Thearyl group may have a substituent or may not. When such an aryl grouphas a substituent, the substituent of the aryl group is preferably analkyl group having 1 to 4 carbon atoms, specifically, a methyl group, anethyl group, an n-propyl group, an isopropyl group, an n-butyl group, anisobutyl group, an s-butyl group, a t-butyl group and the like can begiven. Among them, the methyl group or the t-butyl group is preferable.In addition, as the fluorenyl group, 9,9-dimethylfluoren-2-yl, orspiro-9,9′-bifluoren-2-yl is preferable.

In the formula, each of R¹ and R² is hydrogen, an alkyl group having 1to 4 carbon atoms, or an aryl group having 6 to 25 carbon atoms. As thealkyl group having 1 to 4 carbon atoms, a methyl group, an ethyl group,an n-propyl group, an isopropyl group, an n-butyl group, an isobutylgroup, an s-butyl group, a t-butyl group and the like are given. As thearyl group having 6 to 25 carbon atoms, a phenyl group, a naphthylgroup, a biphenylyl group, a fluorenyl group and the like are given. Thearyl group may have a substituent or may not. When such an aryl grouphas a substituent, the substituent of the aryl group is preferably analkyl group having 1 to 4 carbon atoms, specifically, a methyl group, anethyl group, an n-propyl group, an isopropyl group, an n-butyl group, anisobutyl group, an s-butyl group, a t-butyl group and the like can begiven. Among them, the methyl group or the t-butyl group is preferable.In addition, as the fluorenyl group, 9,9-dimethylfluoren-2-yl, orspiro-9,9′-bifluoren-2-yl is preferable.

In the formula, each of R³ to R⁵ is hydrogen or an alkyl group having 1to 4 carbon atoms. As the alkyl group having 1 to 4 carbon atoms, amethyl group, an ethyl group, an n-propyl group, an isopropyl group, ann-butyl group, an isobutyl group, an s-butyl group, a t-butyl group andthe like are given.

In the formula, each of R⁶ to R¹⁰ is hydrogen, an alkyl group having 1to 4 carbon atoms, or an aryl group having 6 to 25 carbon atoms. As thealkyl group having 1 to 4 carbon atoms, a methyl group, an ethyl group,an n-propyl group, an isopropyl group, an n-butyl group, an isobutylgroup, an s-butyl group, a t-butyl group and the like are given. As thearyl group having 6 to 25 carbon atoms, a phenyl group, a naphthylgroup, a biphenylyl group, a fluorenyl group and the like are given. Thearyl group may have a substituent or may not. When such an aryl grouphas a substituent, the substituent of the aryl group is preferably analkyl group having 1 to 4 carbon atoms, specifically, a methyl group, anethyl group, an n-propyl group, an isopropyl group, an n-butyl group, anisobutyl group, an s-butyl group, a t-butyl group and the like can begiven. Among them, the methyl group or the t-butyl group is preferable.In addition, as the fluorenyl group, 9,9-dimethylfluoren-2-yl, orspiro-9,9′-bifluoren-2-yl is preferable.

In the formula, each of R¹ and R² is hydrogen, an alkyl group having 1to 4 carbon atoms, or an aryl group having 6 to 25 carbon atoms. As thealkyl group having 1 to 4 carbon atoms, a methyl group, an ethyl group,an n-propyl group, an isopropyl group, an n-butyl group, an isobutylgroup, an s-butyl group, a t-butyl group and the like are given. As thearyl group having 6 to 25 carbon atoms, a phenyl group, a naphthylgroup, a biphenylyl group, a fluorenyl group and the like are given. Thearyl group may have a substituent or may not. When such an aryl grouphas a substituent, the substituent of the aryl group is preferably analkyl group having 1 to 4 carbon atoms, specifically, a methyl group, anethyl group, an n-propyl group, an isopropyl group, an n-butyl group, anisobutyl group, an s-butyl group, a t-butyl group and the like can begiven. Among them, the methyl group or the t-butyl group is preferable.In addition, as the fluorenyl group, 9,9-dimethylfluoren-2-yl, orspiro-9,9′-bifluoren-2-yl is preferable.

In the formula, Ar¹ is an aryl group having 6 to 25 carbon atoms. As thearyl group having 6 to 25 carbon atoms, a phenyl group, a naphthylgroup, a biphenylyl group, a fluorenyl group and the like are given. Thearyl group may have a substituent or may not. When such an aryl grouphas a substituent, the substituent of the aryl group is preferably analkyl group having 1 to 4 carbon atoms, specifically, a methyl group, anethyl group, an n-propyl group, an isopropyl group, an n-butyl group, anisobutyl group, an s-butyl group, a t-butyl group and the like can begiven. Among them, the methyl group or the t-butyl group is preferable.In addition, as the fluorenyl group, 9,9-dimethylfluoren-2-yl, orspiro-9,9′-bifluoren-2-yl is preferable.

In the formula, R¹, R² and R⁶ to R¹⁰ are each hydrogen, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms. As the alkyl group having 1 to 4 carbon atoms, a methyl group, anethyl group, an n-propyl group, an isopropyl group, an n-butyl group, anisobutyl group, an s-butyl group, a t-butyl group and the like aregiven. As the aryl group having 6 to 25 carbon atoms, a phenyl group, anaphthyl group, a biphenylyl group, a fluorenyl group and the like aregiven. The aryl group may have a substituent or may not. When such anaryl group has a substituent, the substituent of the aryl group ispreferably an alkyl group having 1 to 4 carbon atoms, specifically, amethyl group, an ethyl group, an n-propyl group, an isopropyl group, ann-butyl group, an isobutyl group, an s-butyl group, a t-butyl group andthe like can be given. Among them, the methyl group or the t-butyl groupis preferable. In addition, as the fluorenyl group,9,9-dimethylfluoren-2-yl, or spiro-9,9′-bifluoren-2-yl is preferable.

As a specific mode of the stilbene derivatives represented by the abovedescribed general formulas (1) to (8), stilbene derivatives representedby the following structural formulas (9) to (152) are given. Note thatstilbene derivatives of the present invention are not limited to thesemodes.

Stilbene derivatives of the present invention have a feature ofproviding blue emission with excellent color purity and having excellentluminous efficiency.

Embodiment Mode 2

[Synthesis Method of the General Formula (1)]

Hereinafter, an example of a synthesis method for a stilbene derivativeof the present invention represented in the following general formula(1) is disclosed.

[Step 1: Synthesis of a Stilbene Derivative (St1) Whose 4-Position isHalogenated]

As represented by the following synthesis scheme (A), by reactingbenzyltriphenylphosphonium salt (α1) whose 4-position is halogenatedwith benzaldehydes (β1) under the presence of a base, so-called, Wittigreaction, a stilbene derivative (St1) whose 4-position is halogenated isobtained. This stilbene derivative (St1) can also be obtained byHorner-Emmons reaction in which phosphonate ester (α2) is used insteadof the triphenylphosphonium salt (α1), as shown in a synthesis scheme(A′). As the base, inorganic bases such as potassium carbonate or sodiumcarbonate, organic bases such as metal alkoxide, or the like can beused.

In addition, the stilbene derivative (St1) can also be obtained as shownby a synthesis scheme (A″) by a Wittig reaction in whichbenzyltriphenylphosphonium salt (α3) which is unsubstituted or at leastone of third, fourth and fifth position of which is substituted andbenzaldehyde (β2) whose 4-position is halogenated are reacted under thepresence of a base. Alternatively, as shown by a synthesis scheme (A′″),this can be obtained by Horner-Emmons reaction in which phosphonateester (α4) is used instead of the triphenylphosphonium salt (α3).

[Step 2: Synthesis of 3-Aminocarbazole Derivative (Cz1)]

Next, as shown by a synthesis scheme (B) below, a 3-aminocarbazolederivative (Cz1) is obtained by coupling a carbazole derivative (γ1)whose third position is halogenated and arylamine under the presence ofa base using a metal catalyst. As the metal catalyst at the coupling, apalladium catalyst such as palladium acetate,tetrakis(triphenylphosphine)palladium, orbis(dibenzylideneacetone)palladium, or monatomic copper can be used. Asthe base, inorganic bases such as potassium carbonate or sodiumcarbonate, organic bases such as metal alkoxide, or the like can beused.

[Step 3: Synthesis of a Stilbene Derivative of the Present InventionRepresented by the General Formula (1)]

Next, as shown by the following synthesis scheme (C), a stilbenederivative of the present invention represented by the general formula(1) can be obtained by coupling the stilbene derivative (St1) obtainedin Step 1 and the 3-aminocarbazole derivative (Cz1) obtained in Step 2under the presence of a base using a metal catalyst. As the metalcatalyst and the base, the above described substances can be used.

[Synthesis Method of the General Formula (3)]

Hereinafter, a synthesis method of a stilbene derivative of the presentinvention represented by the following general formula (3) is shown asone example.

[Step 1: Synthesis of a Stilbene Derivative (St2) Whose 4-Position and4′-Position are Halogenated]

As shown by the following synthesis scheme (D), a stilbene derivative(St2) whose 4-position and 4′-position are halogenated is obtained firstby reacting benzyltriphenylphosphonium salt (α5) whose 4-position ishalogenated with benzaldehyde (β3) whose 4-position is halogenated underthe presence of a base, so-called Wittig reaction. Alternatively, asrepresented by the synthesis scheme (D′), this can be obtained by aHorner-Emmons reaction in which phosphonate ester (α6) is used in steadof the triphenylphosphonium salt (α5).

[Step 2: Synthesis of 3-Aminocarbazole Derivative (Cz1)]

Next, 3-aminocarbazole derivative (Cz1) is synthesized in accordancewith the synthesis scheme (B).

[Step 3: Synthesis of a Stilbene Derivative of the Present InventionRepresented by the General Formula (3)]

Next, as shown by the following synthesis scheme (E) below the stilbenederivative of the present invention represented by the general formula(1) can be obtained by coupling the stilbene derivative (St2) whose4-position and 4′-position are halogenated with the 3-aminocarbazolederivative (Cz1) under the presence of a base using a metal catalyst. Asthe metal catalyst and the base, the above described substances can beused.

[Synthesis Method of the General Formula (5)]

Hereinafter, a synthesis method of a stilbene derivative of the presentinvention represented by the following general formula (5) is shown asone example.

[Step 1: Synthesis of a Stilbene Derivative (St1) Whose 4-Position isHalogenated]

In accordance with any one of the above described synthesis schemes (A)to (A′″), a stilbene derivative (St1) whose 4-position is halogenated issynthesized.

[Step 2: Synthesis of 9-(4-Aminophenyl)Carbazole Derivative (Cz2)]

Next, as shown by the following synthesis scheme (F) below,9-(4-aminophenyl)carbazole derivative (Cz2) is obtained by coupling9-phenylcarbazole derivative (γ2) in which the 4-position of a phenylgroup is halogenated, with arylamine under the presence of a base usinga metal catalyst. As the metal catalyst and the base, the abovedescribed substances can be used.

[Step 3: Synthesis of a Stilbene Derivative of the Present InventionRepresented by the General Formula (5)]

Next, as shown by the following synthesis scheme (G) below, a stilbenederivative of the present invention represented by the general formula(5) can be obtained by coupling a stilbene derivative (St1) whose4-position is halogenated, with 9-(4-aminophenyl)carbazole derivative(Cz2) under the presence of a base using a metal catalyst.

[Synthesis Method of the General Formula (7)]

Hereinafter, a synthesis method of a stilbene derivative of the presentinvention represented by the following general formula (7) is shown asone example.

[Step 1: Synthesis of a Stilbene Derivative (St2) Whose 4-Position and4′-Position are Halogenated]

In accordance with any one of the above described synthesis schemes (D)to (D′), a stilbene derivative (St2) whose 4-position and 4′-positionare halogenated is synthesized.

[Step 2: Synthesis of 9-(4-Aminophenyl)Carbazole Derivative (Cz2)]

9-(4-aminophenyl)carbazole derivative (Cz2) is synthesized in accordancewith the above described synthesis scheme (F).

[Step 3: Synthesis of a Stilbene Derivative of the Present InventionRepresented by the General Formula (7)]

Next, as shown by the following synthesis scheme (H) below, a stilbenederivative of the present invention represented by the general formula(7) can be obtained by coupling the stilbene derivative (St2) whose4-position and 4′-position are halogenated, with the9-(4-aminophenyl)carbazole derivative (Cz2) under the presence of a baseusing a metal catalyst.

Embodiment Mode 3

In accordance with the present invention, a light-emitting element canbe formed using a stilbene derivative as shown in Embodiment Mode 1.

A light-emitting element of the present invention includes an elementstructure in which a layer including a luminescent substance 103 issandwiched between a first electrode 101 and a second electrode 102 asshown in FIG. 1. The layer including a luminescent substance 103includes a stilbene derivative of the present invention. Here, a case isdescribed that the first electrode serves as an anode and the secondelectrode serves as a cathode. Note that the anode is an electrode whichinjects holes into the layer including a luminescent substance and thecathode is an electrode which injects electrons into the layer includinga luminescent substance.

A structure of the layer including a luminescent substance 103 includesat least a light-emitting layer. As examples of the structure, a stackedstructure of a hole injecting layer, a light-emitting layer, and anelectron transporting layer in this order, a stacked structure of a holeinjecting layer, a hole transporting layer, a light-emitting layer, andan electron transporting layer in this order; a stacked structure of ahole injecting layer, a hole transporting layer, a light-emitting layer,a hole-blocking layer and an electron transporting layer in this order;a stacked structure of a hole injecting layer, a hole transportinglayer, a light-emitting layer, a hole-blocking layer, an electrontransporting layer and an electron injecting layer in this order, andthe like are given. The stilbene derivative of the present invention ispreferably used for the light-emitting layer.

The light-emitting element of the present invention is preferablysupported over a substrate. The substrate is not particularly limitedand those used for conventional light-emitting elements can be employed,including substrates made of glass, quartz, transparent plastic or thelike.

As for anode material for the light-emitting element of the presentinvention, use of a metal, an alloy or an electroconductive compoundhaving a high work function (work function of 4.0 eV or more), or amixture thereof is preferred. Specific examples of the anode materialinclude gold (Au), platinum (Pt), titanium (Ti), nickel (Ni), tungsten(W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper(Cu), palladium (Pd), nitride of metal material (TiN) or the like, inaddition to ITO (indium tin oxide), and IZO (indium zinc oxide)including silicon oxide in which indium oxide is mixed with 2 to 20atomic % of zinc oxide (ZnO).

On the other hand, as for a cathode material, use of metals, alloys orelectroconductive compounds having a low work function (work function of3.8 eV or less), or mixtures thereof are preferred. Specific examples ofthe cathode material include, in addition to elements in groups I or IIof the periodic table of the elements, i.e., alkaline metals such as Liand Cs, alkaline earth metals such as Mg, Ca and Sr, and alloys (Mg:Ag,Al:Li) and compounds (LiF, CsF, CaF₂) containing these, transitionmetals including rare earth metals, and further laminates with metals(including alloys) such as Al, Ag or ITO.

However, in a case that a first buffer layer is provided to be incontact with the anode on the light-emission side of the anode, an ohmiccontact with an electrode material having a wide range of work functionis possible. Thus, aluminum (Al), silver (Ag), an alkali metal, analkaline-earth metal such as magnesium (Mg), an alloy thereof (Mg:Ag,Al:Li) or the like which are commonly known as materials having a lowwork function, can be used as an anode material.

The first buffer layer used here is formed from a metal compound and anyone of organic compounds such as an aromatic amine compound, a carbazolederivative, aromatic hydrocarbon including aromatic hydrocarbonincluding at least one vinyl skeleton.

As the aromatic amine compound described above, for example,4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbrev.: NPB);4,4′-bis[N-(3-methylphenyl)-N-phenylamino]biphenyl (abbrev.: TPD);4,4′,4″-tris(N,N-diphenylamino)triphenylamine (abbrev.: TDATA);4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (abbrev.:MTDATA);4,4′-bis(N-{4-[N,N-bis(3-methylphenyl)amino]phenyl}-N-phenylamino)biphenyl(abbrev.: DNTPD); 1,3,5-tris[N,N-di(m-tolyl)amino]benzene (abbrev.:m-MTDAB); 4,4′,4″-tri(N-carbazolyl)triphenylamine (abbrev.: TCTA);2,3-bis(4-diphenylaminophenyl)quinoxaline (abbrev.: TPAQn);2,2′,3,3′-tetrakis(4-diphenylaminophenyl)-6,6′-bisquinoxaline (abbrev.:D-TriPhAQn);2,3-bis{-4-[N-(1-naphthyl)-N-phenylamino]phenyl}dibenzo[f,h]quinoxaline(abbrev.: NPADiBzQn); and the like can be given.

As the carbazole derivative, for example,3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbrev.:PCzPCA1);3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbrev.: PCzPCA2); N-(2-naphthyl)carbazole (abbrev.: NCz);4,4′-di(N-carbazolyl)biphenyl (abbrev.: CBP);9,10-bis[4-(N-carbazolyl)phenyl]anthracene (abbrev.: BCPA);3,5-bis[4-(N-carbazolyl)phenyl]biphenyl (abbrev.: BCPBi);1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbrev.: TCPB) and the likecan be given.

As the aromatic hydrocarbon (including an aromatic hydrocarbon includingat least one vinyl skeleton), aromatic hydrocarbons such as anthracene,9,10-diphenylanthracene (abbrev.: DPA);2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbrev.: t-BuDNA);tetracene; rubrene; pentacene; and 4,4′-bis(2,2-diphenylvinyl)biphenyl(abbrev.: DPVBi) can be given.

As the above-described metal compound, an oxide or nitride of atransition metal is preferable, and an oxide or nitride of a metal whichbelongs to Group 4 to 8 is more preferable. In addition, a materialhaving an electron-accepting property with respect to all of theabove-described aromatic amines, carbazole derivatives, and aromatichydrocarbons (including aromatic hydrocarbons including at least onevinyl skeleton) is preferable. As a metal compound like this, forexample, a metal compound such as molybdenum oxide, vanadium oxide,ruthenium oxide, rhenium oxide, titanium oxide, chromium oxide,zirconium oxide, hafnium oxide, tantalum oxide, tungsten oxide, orsilver oxide can be used.

In the first buffer layer, the metal compound is preferably contained inan organic compound such as an aromatic amine, a carbazole derivative,or an aromatic hydrocarbon (including an aromatic hydrocarbon includingat least one vinyl skeleton) such that a mass ratio is 0.5 to 2 withrespect to these, or a molar ratio is 1 to 4 (=metal compound/organiccompound). In addition, the first buffer layer may have a thickness of50 nm or more, because it has a high conductivity.

On the other hand, as a cathode metal, a metal, an alloy, a conductivecompound having a low work function (work function of 3.8 eV or less),or a mixture thereof is preferably used. As specific example of thecathode material, an element belonging to Group 1 or 2 of the periodictable, in other words, an alkali metal such as Li or Cs, an alkalineearth metal such as Mg, Ca or Sr, an alloy (Mg:Ag, Al:Li) or a compound(LiF, CsF, or CaF₂), a transition metal including a rare earth metal,and further, a stack of metals (including an alloy) such as Al, Ag andITO (indium tin oxide) can be used.

However, when a second buffer layer is provided to be in contact withthe cathode on a light-emitting layer side of the cathode, an ohmiccontact with an electrode material having a work function in the widerange is possible, and thus, ITO (indium tin oxide), indium tin oxideincluding silicon oxide, IZO (indium zinc oxide) including silicon oxidein which indium oxide is mixed with zinc oxide (ZnO) of 2 to 20 atomic%, and the like which are known to be a material with a high workfunction, can be used as the cathode material.

Furthermore, the second buffer layer used here is constituted by acombination of at least one substance selected from electrontransporting substances and bipolar substances, and a substance showingan electron-donating property to these materials (donor). As theelectron transporting substance and the bipolar substance, a substancehaving an electron mobility of 1×10⁻⁶ cm²/Vs or more is preferable. Inaddition, materials to be described below can be used for each of theelectron transporting substance and the bipolar substance.

An anode and a cathode are made of the anode material and the cathodematerial described above, respectively, by forming a thin film by anevaporation method, a sputtering method, or the like. Each of the anodeand the cathode preferably has a thickness of 10 to 500 nm.

The light-emitting element of the present invention has a structure inwhich light generated by recombination of carriers in the layerincluding a luminescent substance is emitted outside from one or both ofthe anode and the cathode. In other words, the anode is made of amaterial having a light transmitting property in a case where light ismade to be emitted through the anode. The cathode is made of a materialhaving a light transmitting property in a case where light is made to beemitted through the cathode.

For the layer including a luminescent substance, known materials can beused, and any of low molecular compounds and high molecular compoundscan be used. The materials for forming the layer including a luminescentsubstance may include not only an organic compound but also an inorganiccompound included in a portion of the layer including a luminescentsubstance.

The layer including the luminescent substance is formed by combininglayers such as the first buffer layer and the second buffer layerdescribed above as well as a hole injecting layer including a holeinjecting substance, a hole transporting layer including a holetransporting substance or a bipolar substance, a light-emitting layerincluding a luminescent substance, a hole blocking layer including ahole blocking substance, an electron transporting layer including anelectron transporting substance, and an electron injecting layerincluding an electron injecting substance.

In the present invention, in the case of using the stilbene derivativefor the light-emitting layer, the layer including a luminescentsubstance interposed between a pair of electrodes can be formed bycombining the light-emitting layer and another layer (for example, thehole injecting layer, the hole transporting layer, the hole blockinglayer; the electron transporting layer, the electron injecting layer,the first buffer layer and the second buffer layer), and thus, alight-emitting element can be formed. Here are shown specific substancesto be used in this case. Description of the first buffer layer and thesecond buffer layer is omitted here, because it has been describedabove.

The hole injecting layer is preferably formed using a hole injectingsubstance. As the hole injecting substance, porphyrin-based compoundsare efficient among organic compounds. For example, phthalocyanine(hereinafter, referred to as H₂-Pc), copper phthalocyanine (hereinafter,referred to as Cu-Pc), or the like can be used. In addition, achemically doped conductive high molecular compound such as polyethylenedioxythiophene (hereinafter, referred to as PEDOT) doped withpolystyrene sulfonate (hereinafter, referred to as PSS).can be used.

The hole transporting layer is a layer superior in a hole transportingproperty, and specifically, the hole transporting layer is preferablyformed of a hole transporting substance or a bipolar substance, whichhas hole mobility of 1×10⁻⁶ cm²/Vs or more. The hole transportingsubstance is a substance having higher hole mobility than electronmobility, and preferably, a substance having a value of a ratio of thehole mobility to the electron mobility (=hole mobility/electronmobility) of more than 100.

As the hole transporting substance, for example, an aromatic amine-based(namely a substance having a bond of benzene ring-nitrogen) nitrogen)compound is preferable. As a substance which is widely used, forexample, 4,4′-bis[N-(3-methylphenyl)-N-phenylamino]biphenyl(hereinafter, referred to as TED);4,4′-bis[N-(1-naphtyl)-N-phenyl-amino]biphenyl (hereinafter, referred toas NPB) which is a derivative thereof; a star burst aromatic aminecompound such as 4,4′,4″-tris(N-carbazolyl)-triphenylamine (hereinafter,referred to as TCTA); 4,4′,4″-tris(N,N-diphenylamino)triphenylamine(hereinafter, referred to as TDATA); or4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine(hereinafter, referred to as MTDATA) is given.

The bipolar substance is a substance which is described as follows: whenmobility of an electron and mobility of a hole are compared with eachother, a value of a ratio of mobility of one carrier to mobility of theother carrier is 100 or less, preferably 10 or less. As the bipolarsubstance, for example, 2,3-bis(4-diphenylaminophenyl) quinoxaline(abbrev.: TPAQn);2,3-bis{-4-[N-(1-naphthyl)-N-phenylamino]phenyl}dibenzo[f,h]quinoxaline(abbrev.: NPADiBzQn); and the like are given. In particular, amongbipolar substances, a substance having hole mobility and electronmobility of 1×10⁻⁶ cm²/Vs or more is preferably used.

The light-emitting layer includes at least one kind of luminescentsubstance. A luminescent substance herein represents a substance withexcellent luminous efficiency which can emit light of a desiredwavelength. The light emitting layer is a layer in which a stilbenederivative is mixed to be dispersed in a layer made of a substance (hostsubstance) having a larger band gap (the energy gap between a LUMO leveland a HOMO level) than a band gap of the stilbene derivative sewing as aguest substance, as an aspect of the present invention (in other words,a layer including a host substance and a guest substance).

Thus, by using a stilbene derivative of the present invention to alight-emitting layer, blue emission with excellent color purity can beobtained.

As a host substance which is combined with a stilbene derivative of thepresent invention to form a light-emitting layer,9-[4-(N-carbazolyl)phenyl]-10-phenyl anthracene (abbrev.: CzPA),4,4′-di(N-carbazolyl)biphenyl (abbrev.: CBP),bis[2-(2-hydroxyphenyl)benzoxazolato]zinc (abbrev.: Zn(BOX)₂),9,10-di(2-naphthyl)anthracene (abbrev.: DNA),4,4′,4″-tri(N-carbazolyl)triphenylamine (abbrev.: TCTA),2,2′,2″-(1,3,5-benzenetriyl)-tris(1-phenyl-1H-benzimidazole) (abbrev.:TPBi) or the like can be used.

The electron transporting layer is a layer which is superior in anelectron transporting property, and specifically, the electrontransporting layer is preferably formed of an electron transportingsubstance or a bipolar substance, which has electron mobility of 1×10⁻⁶cm²/Vs or more. The electron transporting substance is a substancehaving higher electron mobility than hole mobility, and preferably, asubstance having a value of a ratio of the electron mobility to the holemobility (=electron mobility/hole mobility) of more than 100.

As a specific electron transporting substance, a metal complex having aquinoline skeleton or a benzoquinoline skeleton such astris(8-quinolinolato)aluminum (hereinafter, Alq₃),tris(4-methyl-8-quinolinolato)aluminum (hereinafter, Almq₃), orbis(10-hydroxybenzo[h]-quinolinato)beryllium (hereinafter, BeBq₂);bis(2-methyl-8-quinolinolato)(4-phenylphenolate)aluminum (hereinafter,BAlq) which is a mixed ligand complex; or the like is preferable. Inaddition, a metal complex having an oxazole-based or thiazole-basedligand such as bis[2-(2-hydroxyphenyl)benzoxazolato]zinc (hereinafter,Zn(BOX)₂) or bis[2-(2-hydroxyphenyl)benzothiazolato]zinc (Zn(BTZ)₂) canalso be used. Furthermore, an oxadiazole derivative such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (hereinafter,referred to as PBD) or1,3-bis[5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene(hereinafter, referred to as OXD-7); a triazole derivative such as3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole(hereinafter, referred to as TAZ) or3-(4-biphenylyl)-4-(4-ethylphenyl)-5-(4-tert-butylphenyl)-1,2,4-triazole(hereinafter, referred to as p-EtTAZ); a phenanthroline derivative suchas bathophenanthroline (hereinafter, referred to as BPhen) orbathocuproin (hereinafter, referred to as BCP); and, in addition,4,4-bis(5-methylbenzoxazolyl-2-yl)stilbene (hereinafter, referred to asBzOs); or the like can be used as well as the metal complexes describedabove. It is to be noted that the substances described above can be usedas the bipolar substance.

In addition, as a hole blocking substance, BAlq, OXD-7, TAZ, p-EtTAZ,BPhen, BCP or the like which has been described above can be used.

As described above, by forming a light-emitting element with alight-emitting layer using a stilbene derivative of the presentinvention, a blue light-emitting element with excellent color purity canbe obtained. Further, a light-emitting element with excellent luminousefficiency can be obtained. Moreover, a long lifetime light-emittingelement can be obtained.

Embodiment Mode 4

In Embodiment Mode 4, as an example of a thin film transistor (TFT)which can be combined with a light-emitting element including a stilbenederivative of the present invention to manufacture a light-emittingdevice, a single gate TFT having a top gate structure will be describedwith reference to FIG. 2.

As shown in FIG. 2, a TFT 208 is formed over a substrate 201. A drainelectrode 207 b of the TFT 208 is electrically connected to a firstelectrode 209 of a light-emitting element. A second electrode is formedover the first electrode 209 with a layer including a luminescentsubstance therebetween and thus, the light-emitting element as describedin Embodiment Mode 2 is formed. Accordingly, the 208 can control drivingof the light-emitting element.

There is no particular limitation on the substrate 201, and flexiblematerials such as polyethyleneterephthalate (PET),polyethylenenaphthalate (OEN), or polyethersulfone (PES) can be used, inaddition to glass, quartz, or the like.

In addition, although not shown here, an insulating film formed of aninsulator such as silicon oxide or silicon nitride may be formed overthe substrate 201 by a known film-formation method such as plasma CVD orsputtering. Note that the insulating film may be formed to have a singlelayer structure or a multilayer structure in which plural layers arestacked. By providing an insulating film between the substrate 201 andthe TFT 208, impurities can be prevented from diffusing into the TFT 208from the substrate 201.

A source region 202 a, a drain region 202 b and a channel forming region203 in FIG. 2 are formed from a semiconductor film: As the semiconductorfilm, any of an amorphous semiconductor film having different crystalstates, an amorphous semiconductor film including partially a crystalstate, and a crystalline semiconductor film, which mainly includesilicon, silicon-germanium (SiGe) or the like can be used. In thisembodiment mode, the crystalline semiconductor film is used. Inaddition, the semiconductor film can be formed by a known method such asplasma CVD or sputtering. A thickness of the semiconductor film ispreferably 10 to 150 nm, preferably, 30 to 70 nm.

The crystalline semiconductor film can be formed by crystallizing anamorphous semiconductor film by heating or laser irradiation.Alternatively, a crystalline semiconductor film can be formedoriginally. Specifically, a crystalline semiconductor film can be formedby heat or plasma using a fluorine-based gas such as GeF₄ or F₂, and asilane-based gas such as SiH₄ or Si₂H₆.

The source region 202 a and the drain region 202 b are regions in whichan impurity element is added into the crystalline semiconductor film.The impurity element is an element which can impart one conductivity tothe semiconductor film, typically, phosphorus (P) or the like is givenas an impurity element imparting an n-type conductivity, and boron (B)or the like is given as an impurity element imparting a p-typeconductivity. When the first electrode 209 serves as an anode, animpurity element imparting the p-type conductivity is preferably added.On the other hand, when the first electrode 209 serves as a cathode, animpurity element imparting the n-type conductivity is preferably added.In the TFT structure shown in this embodiment mode, after forming acrystalline semiconductor film, an impurity element is added into thecrystalline semiconductor film by using a gate electrode 205 to beformed later as a mask.

A gate insulating film 204 formed to cover the source region 202 a, thedrain region 202 b and the channel forming region 203 is formed using aninsulator such as silicon oxide, silicon nitride, silicon oxynitride, orsilicon nitride oxide by a film-formation method such as plasma CVD orsputtering. The gate insulating film 204 may be formed to have a singlelayer structure of insulating film or a multilayer structure in whichplural insulating films are stacked. A thickness of the gate insulatingfilm 204 is preferably 10 to 150 nm, preferably, 30 to 70 nm.

The gate electrode 205 can be formed using a conductive film made of ametal nitride such as tantalum nitride (TaN) or titanium nitride (TN),in addition to a metal such as tungsten (W), aluminum (Al), molybdenum(Mo), tantalum (Ta), titanium (Ti), copper (Cu), chromium (Cr) orniobium (Nb). In addition, the gate electrode 205 may be formed to havea single layer of conductive film or a multilayer structure in whichplural conductive films are stacked. In addition, the conductive filmcan be formed by a known film-formation method such as sputtering. Athickness of the gate electrode 205 is preferably 200 nm or more, morepreferably 300 to 700 nm.

An interlayer insulating film 206 formed to cover the source region 202a, the drain region 202 b, the channel forming region 203 and the gateelectrode 205 can be formed using an insulator such as silicon oxide,silicon nitride, silicon oxynitride or silicon nitride oxide. Besides,an insulator such as acrylic, polyimide, or siloxane can be used. Notethat the siloxane is a compound including an element such as silicon(Si), oxygen (O) or hydrogen (H) and further including Si—O—Si bond(siloxane bond). Note that the insulating film described above can beformed by a known film-formation method such as a plasma CVD method, asputtering method, an application method, or a spin coating method. Notethat a thickness of the interlayer insulating film 206 is preferably 300nm to 2 μm, further preferably, 500 nm to 1 μm.

A source electrode 207 a and a drain electrode 207 b formed over theinterlayer insulating film 206 are electrically connected to the sourceregion 202 a and the drain region 202 b, respectively. As the sourceelectrode 207 a and the drain electrode 207 b, a film formed of a metalelement such as silver (Ag), gold (Au), copper (Cu), nickel (Ni),platinum (Pt), palladium (Pd), iridium (It), ruthenium (Ru), tungsten(W), aluminum (Al), tantalum (Ta), molybdenum (Mo), cadmium (Cd), zinc(Zn), iron (Fe), titanium (Ti), silicon (Si), germanium (Ge), zirconium(Zr), or barium (Ba); a film formed of an alloy material containing someof the above-described elements as its main component (for example, analloy including Al, carbon (C) and Ni; or an alloy including Al, carbon(C) and Mo); or a stacked film including some of the above elements (forexample, a stacked film of Mo, Al and Mo, a stacked film of Ti, Al, andTi, or a stacked film of Ti, titanium nitride (TN), Al and Ti); a filmmade of a compound material such as a metal nitride; or the like can begiven. The above described conductive film can be formed by a knownfilm-formation method such as sputtering. Thicknesses of the sourceelectrode 207 a and the drain electrode 207 b are preferably 200 nm ormore, more preferably, 300 to 700 nm.

In addition, the drain electrode 207 b is electrically connected to thefirst electrode 209 of the light-emitting element. The material forforming the first electrode 209 has been described in Embodiment Mode 3and the description in Embodiment Mode 3 may be referred to. Descriptionof the material for forming the first electrode 209 is omitted here.

An insulator 210 is formed to cover the source electrode 207 a, thedrain electrode 207 b and an end portion of the first electrode 209.Further, the insulator 210 is preferably formed to have a curvature onits side. The insulator 210 can be formed using acrylic, polyimide,resist, silicon oxide, silicon nitride, siloxane or the like.

This embodiment mode has described the case where the TFT 208 is asingle gate type TFT having a top gate structure; however, is notlimited to this case. A 111 having a bottom gate structure or amultigate type having plural gate electrodes may be used. Further, a TFThaving an LDD (lightly doped drain) structure in which a lowconcentration impurity region including an impurity element at lowerconcentration than a drain region is formed, between a channel formingregion and a drain region, may be employed. Furthermore, a transistorwith a gate-overlapped LDD structure in which a low concentrationimpurity region formed between a channel forming region and a drain isoverlapped with a gate electrode, may be used.

By using a TFT described above and a light-emitting element including astilbene derivative of the present invention in combination so as tomanufacture a light-emitting device, a longer life light-emitting devicewith excellent luminous efficiency as well as blue emission withexcellent color purity can be provided.

Embodiment Mode 5

In Embodiment Mode 5, as an example of a thin film transistor (TFT)which can be combined with a light-emitting element including a stilbenederivative of the present invention to manufacture a light-emittingdevice, a channel-etch type TFT having a bottom gate structure will bedescribed with reference to FIG. 3A and a channel-stopped type TFThaving a bottom gate structure will be described with reference to FIG.3B.

As shown in FIG. 3A, a channel-etch type TFT having a bottom gatestructure 308 is formed over a substrate 301. A drain electrode 306 b ofthe TFT 308 is electrically connected to a first electrode 309 of alight-emitting element. A second electrode is formed over the firstelectrode 309 with a layer including a luminescent substancetherebetween and thus, the light-emitting element as described inEmbodiment Mode 3 is formed. Accordingly, the TFT 308 can controldriving of the light-emitting element.

There is no particular limitation on the substrate 301, and the samematerials as the substrate 201 shown in Embodiment Mode 3 can be used.In addition, an insulating film which can be formed between thesubstrate 301 and the TFT 308 can be formed by the same method and usingthe same material as in Embodiment Mode 4. Note that the effect is thesame.

A gate electrode 302 is formed over the substrate 301. A gate insulatingfilm 303 is formed over the gate electrode 302. Note that the gateelectrode 302 and the gate insulating film 303 can be formed by the samemethod and using the same material as the gate electrode 205 and thegate insulating film 204 in Embodiment Mode 4, respectively.

Over a portion where the gate electrode 302 is overlapped with the gateinsulating film 303, a channel forming region 304 made of a firstsemiconductor film is formed. As the first semiconductor film, any of anamorphous semiconductor film, an amorphous semiconductor film includingpartially a crystal state, and a crystalline semiconductor film, whichmainly include silicon, silicon-germanium (SiGe) or the like can beused. In this embodiment mode, an amorphous semiconductor film is usedas the first semiconductor film. In addition, the first semiconductorfilm can be formed by a known method such as plasma CVD or sputtering. Athickness of the first semiconductor film is preferably 10 to 150 nm,more preferably, 30 to 70 nm.

A source region 305 a and a drain region 305 b made of a secondsemiconductor film are formed over the first semiconductor film. As thesecond semiconductor film, any of an amorphous semiconductor film, anamorphous semiconductor film including partially a crystal state, and acrystalline semiconductor film, which mainly include silicon,silicon-germanium (SiGe) or the like and includes an impurity elementimparting an n-type or a p-type conductivity, can be used. In thisembodiment mode, an amorphous semiconductor film is used as the secondsemiconductor film. The semiconductor film is an amorphous semiconductorfilm including beforehand an impurity element imparting an n-type orp-type conductivity. In addition, the second semiconductor film can beformed by a known method such as plasma CVD or sputtering. A thicknessof the second semiconductor film is preferably 10 to 150 nm, morepreferably, 30 to 70 nm.

A source electrode 306 a is formed on and in contact with the sourceregion 305 a and a drain electrode 306 b is formed on and in contactwith the drain region 305 b. Note that the source electrode 306 a andthe drain electrode 306 b are formed by the same method, using the samematerial and with the same thickness as the source electrode 207 a andthe drain electrode 207 b shown in Embodiment Mode 3.

The TFT 308 as described above includes the gate electrode 302, the gateinsulating film 303, the channel forming region 304, the source region305 a, the drain region 305 b, the source electrode 306 a, and the drainelectrode 306 b, and an interlayer insulating film 307 is formed tocover the TFT 308. Note that the interlayer insulating film 307 can beformed using the same material as the interlayer insulating film 206shown in Embodiment Mode 3.

The drain electrode 306 b is electrically connected to the firstelectrode 309 of the light-emitting element through an opening portionwhich is formed in a part of the interlayer insulating film 307. Themethod, material and thickness for forming the first electrode 309 havebeen described in Embodiment Mode 3 and the description in EmbodimentMode 3 may be referred to. Description of the method, material andthickness for forming the first electrode 309 is omitted here.

An insulator 310 formed to cover the TFT 308 and an end portion of thefirst electrode 309 can be formed by the same method, using the samematerial and with the same thickness as the insulator 310 shown inEmbodiment Mode 3.

A channel-stop type TFT 328 having a bottom gate structure has thestructure as shown in FIG. 3B. In other words, the TFT 328 is formedover a substrate 321, and a drain electrode 326 b of the TFT 328 iselectrically connected to the first electrode 329 of the light-emittingelement. A second electrode is formed over the first electrode 329 witha layer including a luminescent substance therebetween and thus, thelight-emitting element as described in Embodiment Mode 2 is formed.Accordingly, the TFT 328 can control driving of the light-emittingelement.

In the channel-stop type TFT 328 having a bottom gate structure shown inFIG. 3B, a protective film 331 is provided over the channel formingregion 324, in a position which is overlapped with the gate electrode.

Note that the protective film 331 is a film having a function ofprotecting the first semiconductor film in order to prevent the firstsemiconductor film forming the channel forming region 324 from beingetched when the second semiconductor film and the conductive film areprocessed to form the source region 325 a, the drain region 325 b, thesource electrode 326 a, and the drain electrode 326 b. The protectivefilm 331 may be formed of an insulating film such as silicon oxide,silicon nitride, silicon oxynitride or silicon nitride oxide by afilm-formation method such as plasma CVD or sputtering.

In addition, in the TFT 328 shown in FIG. 3B, the gate electrode 322,the gate insulating film 323, the channel forming region 324, the sourceregion 325 a, the drain region 325 b, the source electrode 326 a, thedrain electrode 326 b, the interlayer insulating film 327, the firstelectrode 329 and the insulator 330 may be formed by the same method,using the same material and with the same thickness as the gateelectrode 302, the gate insulating film 303, the channel forming region304, the source region 305 a, the drain region 305 b, the sourceelectrode 306 a, the drain electrode 306 b, the interlayer insulatingfilm 307, the first electrode 309 and the insulator 310 shown in FIG.3A, and thus, description made in FIG. 3A is referred to, anddescription of the method, material and thickness thereof is omittedhere.

By using a TFT as described above and a light-emitting element includinga stilbene derivative of the present invention in combination so as tomanufacture a light-emitting device, a longer life light-emitting devicewith excellent luminous efficiency as well as blue emission withexcellent color purity can be provided.

Embodiment Mode 6

In Embodiment Mode 6, a light-emitting device having the light-emittingelement of the present invention in a pixel portion will be describedwith reference to FIGS. 4A and 4B. Note that the structure of alight-emitting device of the present invention includes a control meanssuch as a driver circuit for driving the light-emitting element, as wellas the light-emitting element in accordance with the present invention.FIG. 4A is a top view showing the light-emitting device, and FIG. 4B isa sectional view taken along the section A-A′ of FIG. 4A. A sourcedriver circuit is denoted by Reference numerals 401, 402 and 403, whichare shown by a dotted line; denote a driver circuit portion (a sourcedriver circuit), a pixel portion, and a driver circuit portion (a gatedriver circuit), respectively. Reference numeral 404 denotes a sealingsubstrate; reference numeral 405 denotes a sealant; and an inner sideregion enclosed by the sealant 405 is a space 407.

Reference numeral 408 denotes a wire for transmitting signals input tothe source driver circuit 401 and the gate driver circuit 403 andreceives a video signal, a clock signal, a start signal, a reset signal,and the like from an FPC (Flexible Printed Circuit) 409 serving as anexternal input terminal In addition, though only the FPC is indicated inthe drawing, a printed wire board (PWB) may be attached to the FPC. Inthis specification, the light-emitting device includes thelight-emitting device on which the FPC or the PWB is mounted as well asthe light-emitting device itself.

Next, a sectional structure will be described using FIG. 4B. The drivercircuit portion and the pixel portion are formed over a substrate 410.Here, the source driver circuit 401 of the driver circuit portion andthe pixel portion 402 are shown.

As the source driver circuit 401, a CMOS circuit which is obtained bycombining an n-channel ITT 423 and a p-channel TFT 424 is formed. TheTFT forming the driver circuit may be a known CMOS circuit, PMOS circuitor NMOS circuit. Though the driver-integrated type, which the drivercircuit is formed over the substrate, is used in this embodiment mode,the driver circuit may be formed outside the substrate.

The pixel portion 402 is formed of a plurality of pixels having aswitching TFT 411, a current control TFT 412, and a first electrode 413electrically connected to a drain of the current control TFT 412. Aninsulator 414 is formed to cover an end portion of the first electrode413. The insulator 414 is formed by using a positive type photosensitiveacryl resin film.

Over the first electrode 413, a layer including a luminescent substance416 and a second electrode 417 are formed. It is desirable to use amaterial having a high work function as a material for forming the firstelectrode 413 functioning as the anode. For instance, a single layerfilm of an ITO (indium tin oxide) film, an indium zinc oxide (IZO) film,a titanium nitride film, a chromium film, a tungsten film, a Zn film, aPt film, or the like, a stacked film of a film mainly containingtitanium nitride and a film mainly comprising aluminum, a three layerstructure of a titanium nitride film, a film mainly containing aluminum,and a titanium nitride film, or the like may be used. The stackedstructure reduces a wire resistance and achieves a good ohmic contact,so that the stacked structure is capable of functioning as the anode.

The layer including a luminescent substance 416 is formed by anevaporation method using an evaporation mask or an inkjet method. Thelayer including a luminescent substance 416 includes a light-emittinglayer, an electron generating layer, a hole transporting layer, anelectron transporting layer, a hole blocking layer, a hole injectinglayer, an electron injecting layer, a buffer layer or the like. Notethat a low-molecular material, an intermediate-molecular material(including oligomer and dendrimer) or a high-molecular material can beused for forming the above described layers. Further, though a singlelayer of an organic compound or a stack of organic compound layers isgenerally used for the layer including a luminescent substance, thepresent invention includes a structure which an inorganic compound isused for a part of a film formed from an organic compound.

In the present invention, the buffer layer is provided to be in contactwith one electrode of the both electrodes (an anode and a cathode) ofthe light-emitting element, to be in contact with the both electrodes,or to be in contact with neither of the both electrodes.

A second electrode (cathode) 417 is formed over the layer including aluminescent substance 416.

By joining the sealing substrate 404 and the element substrate 410 withthe sealant 405, a structure where the light-emitting element 418 isprovided in the space 407 surrounded by the element substrate 410, thesealing substrate 404, and the sealant 405 is formed. Structures whereinthe space 407 is filled with an inert gas (nitrogen or argon) and thespace 407 is filled with the sealant 405 are included in the presentinvention.

It is preferable to use an epoxy-based resin as the sealant 405. Also,it is desirable that the material to be used should not permeatemoisture and oxygen as much as possible. Further, as a material to beused for the sealing substrate 404, a plastic substrate made from FRP(Fiberglass-Reinforced Plastics), PVF (polyvinyl fluoride), mylar,polyester, or acryl may be used, in addition to a glass substrate, and aquartz substrate.

As described above, by manufacturing a light-emitting device including astilbene derivative of the present invention, a longer lifelight-emitting device with excellent luminous efficiency as well as blueemission with excellent color purity can be provided.

The light-emitting device shown in this embodiment mode can be freelycombined with any of the structures shown in Embodiment Modes 1 to 5.

Embodiment Mode 7

Embodiment Mode 7 will describe examples of electronic devices includinga stilbene derivative with reference to FIGS. 5A to 5E.

A television device shown in FIG. 5A includes a main body 8001, adisplay portion 8002, and the like. In the display portion 8002, each ofpixels includes a light-emitting element in which a stilbene derivativeis included in a layer including a luminescent substance, and the pixelsare arranged in matrix. For example, the light-emitting device ofEmbodiment Mode 6 can be applied to the display portion 8002. By formingthe display portion 8002 including the stilbene derivative, a longerlife television device with excellent luminous efficiency as well asblue color reproductivity and low power consumption can be provided.

A portable information terminal device shown in FIG. 5B includes a mainbody 8101, a display portion 8102, and the like. In the display portion8102, pixels are formed using a light-emitting element in which astilbene derivative is included in a layer including a luminescentsubstance, and the pixels are arranged in matrix. For example, thelight-emitting device of Embodiment Mode 6 can be applied to the displayportion 8102. By forming the display portion 8102 including the stilbenederivative, a longer life portable information terminal device withexcellent luminous efficiency as well as blue color reproductivity andlow power consumption can be provided.

A video camera shown in FIG. 5C includes a main body 8201, a displayportion 8202, and the like. In the display portion 8202, pixels areformed using a light-emitting element in which a stilbene derivative isincluded in a layer including a luminescent substance, and the pixelsare arranged in matrix. For example, the light-emitting device ofEmbodiment Mode 6 can be applied to the display portion 8202. By formingthe display portion 8202 including the stilbene derivative, a longerlife video camera with excellent luminous efficiency as well as bluecolor reproductivity and low power consumption can be provided.

A telephone shown in FIG. 5D includes a main body 8301, a displayportion 8302, and the like. In the display portion 8302, pixels areformed using a light-emitting element in which a stilbene derivative isincluded in a layer including a luminescent substance, and the pixelsare arranged in matrix. For example, the light-emitting device ofEmbodiment Mode 6 can be applied to the display portion 8302. By formingthe display portion 8302 including the stilbene derivative, a longerlife telephone with excellent luminous efficiency as well as blue colorreproductivity and low power consumption can be provided.

A portable television device shown in FIG. 5E includes a main body 8401,a display portion 8402, and the like. In the display portion 8402,pixels are formed using a light-emitting element in which a stilbenederivative is included in a layer including a luminescent substance, andthe pixels are arranged in matrix. For example, the light-emittingdevice of Embodiment Mode 6 can be applied to the display portion 8402.By forming the display portion 8402 including the stilbene derivative, alonger life portable television device with excellent luminousefficiency as well as blue color reproductivity and low powerconsumption can be provided. In addition, the light-emitting device ofthe present invention can be widely applied to various televisiondevices such as a small sized one incorporated in a portable terminalsuch as a cellular phone handset, a medium sized one which is portable,and a large sized one (for example, 40 inches or more in size).

The electronic devices according to the present invention are notlimited to those shown in FIGS. 5A to 5E, and electronic devices inwhich a stilbene derivative is included in a display portion or alight-emitting portion are also included. For example, an electronicdevice in which a light-emitting element including a stilbene derivativeis used as lighting for showing a position of a switch or a status canbe provided. In addition, a light-emitting element including a stilbenederivative can be used for a light-source of a traffic signal machine.

By including a display portion or the like including a stilbenederivative, a longer life electronic device with excellent luminousefficiency as well as blue emission with excellent color purity can beprovided.

Example 1

Hereinafter, Synthesis Examples and Examples of a stilbene derivative ofthe present invention will be described; however, the present inventionis not limited thereto.

Synthesis Example 1

Synthesis Example 1 will describe a synthesis method of4-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]stilbene (abbrev.: PCAS)represented by the structural formula (9), as an example of a stilbenederivative of the present invention.

[Step 1: Synthesis of 4-bromostilbene]

(i) A Synthetic Method of 4-bromobenzyltriphenylphosphoniumbromide isDescribed Below.

First, 25.36 g (101.5 mmol) of 4-bromobenzylbromide and 100 mL ofacetone were put in a 100 mL conical flask, and 29.28 g (111.6 mmol) oftriphenylphosphine was added thereto. The mixture was stirred for 24hours at room temperature. After the reaction, a precipitate in thereaction mixture was collected by suction filtration, and 50 g of awhite powdered solid of 4-bromobenzyltriphenylphosphoniumbromide wasobtained in a yield of 96%.

(ii) A Synthetic Method of 4-bromostilbene is Described Below.

25.3 g (49.5 mmol) of 4-bromobenzyltriphenylphosphoniumbromide, whichwas obtained in (i), and 5.25 g (49.5 mmol) of benzaldehyde were put ina 500 mL conical flask, and nitrogen substitution was carried out. Then,150 mL of dehydrated tetrahydrofuran (abbrev.: THF) was added thereto,and was cooled. Then, 6.10 g (54.4 mmol) of potassium tert-butoxidedissolved in 50 mL, of dehydrated THF was dropped to this, and wasstirred for 24 hours at room temperature. After the reaction, thesolution was washed with water and separated into an organic layer andan aqueous layer. This aqueous layer was extracted with ethyl acetate,and the obtained extraction solution was combined with the organic layerand then dried with magnesium sulfate. Suction filtration of the mixedsolution was carried out, and the filtrate was concentrated. Theobtained residue was washed with methanol, and then a precipitate in themixture was collected by suction filtration, and 3.75 g of a whitesolid, which was the target substance, was obtained in a yield of 29%.

Next, a synthesis scheme (a-1) of 4-bromostilbene is shown.

[Step 2: Synthesis of 3-(N-phenylamino)-9-phenylcarbazole (Abbrev.:PCA)]

(i) A Synthetic Method of 3-bromo-9-phenylcarbazole is Described Below.

First, 24.3 g (100 mmol) of N-phenylcarbazole was dissolved in 600 mL ofgracial acetic acid, and 17.8 g (100 mmol) of N-bromosuccinimide wasslowly added thereto. Then, the mixture was stirred for 24 hours at roomtemperature. This gracial acetic acid solution was dropped into 1 L ofice water while being stirred. The precipitated white solid was washedwith water three times. This solid was dissolved in 150 mL ofdiethylether, and washed with a saturated sodium hydrogen carbonatesolution and water in this order.

This organic layer was dried with magnesium sulfate and then filtratedto obtain a filtrate. The filtrate was concentrated. The obtainedresidue was added with about 50 mL of methanol and was irradiated withultrasonic waves so as to be dissolved uniformly. This solution was leftat rest, and a white solid was precipitated. This solution was filtered,and the precipitate was dried to obtain 28.4 g (in a yield of 88%) of awhite powder, which was 3-bromo-9-phenylcarbazole.

(ii) A Synthetic Method of 3-(N-phenylamino)-9-phenylcarbazole (Abbrev.:PCA) is Described Below.

Under a nitrogen atmosphere, 110 mL of dehydrated xylene and 7.0 g (75mmol) of aniline were added into a mixture containing 19 g (60 mmol) of3-bromo-9-phenylcarbazole obtained in (i), 340 mg (0.6 mmol) ofbis(dibenzylideneacetone)palladium(0) (abbrev.: Pd(dba)₂), 1.6 g (3.0mmol) of 1,1-bis(diphenylphosphino)ferrocene (abbrev.: DPPF) and 13 g(180 mmol) of sodium tert-butoxide (abbrev.: tert-BuONa). This mixedsolution was heated and stirred under a nitrogen atmosphere at 90° C.for 7.5 hours.

After the reaction, about 500 mL of toluene which had been heated to 50°C. was added into this suspension and then, filtered through florisil,alumina and celite. The obtained filtrate was concentrated, andhexane-ethyl acetate was added into this residue, and was irradiatedwith ultrasonic waves. The obtained suspension was filtered, and thisfiltrate was dried to obtain 15 g (in a yield of 75%) of a cream-coloredpowder. By a nuclear magnetic resonance method (¹H NMR), thiscream-colored powder was ascertained to be3-(N-phenylamino)-9-phenylcarbazole (abbrev.: PCA).

Next, ¹H NMR of this compound is shown. In addition, FIGS. 6A and 6Bshow ¹H NMR charts. FIG. 6B is an enlarged chart showing a range of 5ppm to 9 ppm of FIG. 6A.

¹H NMR (300 MHz, CDCl₃); δ=6.84 (t, J=6.9 Hz, 1H), 6.97 (d, J=7.8 Hz,2H), 7.20-7.61 (m, 13H), 7.90 (s, 1H), 8.04 (d, J=7.8 Hz, 1H).

Next, ¹H NMR of this compound is shown. In addition, FIGS. 52A and 52Bshow ¹H NMR charts. FIG. 52B is an enlarged chart showing a range of 6.5ppm to 8.5 ppm of FIG. 52A.

¹H NMR (300 MHz, DMSO-d₆); δ=6.73 (t, J=7.5 Hz, ¹H), 7.02 (d, J=8.1 Hz,2H), 7.16-7.70 (m, 12H), 7.95 (s, 1H), 8.06 (s, 1H), 8.17 (d, J=7.8 Hz).

Further, ¹³C NMR is shown next. In addition, FIGS. 53A and 53B show ¹³CNMR charts. FIG. 53B is an enlarged chart showing a range of 100 ppm to150 ppm of FIG. 53A.

¹³C NMR (75.5 MHz, DMSO-d₆); δ=109.55, 110.30, 110.49, 114.71, 118.22,119.70, 120.14, 120.61, 122.58, 123.35, 126.18, 126.48, 127.37, 129.15,130.14, 135.71, 136.27, 137.11, 140.41, 145.61.

Next, a synthesis scheme (b-1) of 3-(N-phenylamino)-9-phenylcarbazole(abbrev.: PCA) is shown.

[Step 3: Synthesis of4-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]stilbene (Abbrev.: PCAS)]

1.00 g (3.86 mmol) of 4-bromostilbene, 1.29 g (3.86 mmol) of3-(N-phenylamino)-9-phenylcarbazole (abbrev.: PCA), 0.11 g (0.193 mmol)of bis(dibenzylideneacetone)palladium, and 1.85 g (19.3 mmol) of sodiumtert-butoxide were put in a 100 mL three-necked flask, and nitrogensubstitution was carried out. Then, 20 mL of toluene and 0.39 g (0.193mmol) of tri(tert-butyl)phosphine (10% hexane solution) were addedthereto, and heated to be stirred for 7 hours at 80° C.

After the reaction, the solution was washed with water and separatedinto an organic layer and an aqueous layer. This aqueous layer wasextracted with toluene, and the obtained extraction solution was driedwith magnesium sulfate together with the organic layer. The mixedsolution was filtered, and the filtrate was concentrated. The obtainedresidue was purified by silica gel column chromatography (toluene-hexanemixed solution), and the residue was recrystallized with thetoluene-hexane mixed solution to obtain 1.34 g of a yellow solid in ayield of 68%. By a nuclear magnetic resonance method (¹H NMR), thiscompound was ascertained to be4-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]stilbene (abbrev.: PCAS).

¹H NMR of this compound is shown below. In addition, FIG. 7 shows a ¹HNMR chart. ¹H NMR (300 MHz, CDCl₃); δ=7.90 (d, J=7.8 Hz, 1H), 7.94 (s,1H), 7.61-7.31 (m, 14H), 7.25-7.00 (m, 12H)

Next, a synthesis scheme (c-1) of4-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]stilbene (abbrev.: PCAS) isshown.

An absorption spectrum of4-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]stilbene (hereinafterreferred to as PCAS) is shown in FIG. 8. In FIG. 8, the horizontal axisindicates a wavelength (nm) and the vertical axis indicates intensity(no unit). Note that FIG. 8 shows an absorption spectrum in a statewhere PCAS was dissolved in a toluene solution.

An emission spectrum of PCAS is shown in FIG. 9. In FIG. 9, thehorizontal axis indicates a wavelength (nm) and the vertical axisindicates emission intensity (arbitrary unit). Note that FIG. 9 shows anemission spectrum (excitation wavelength: 393 nm) in a state where PCASwas dissolved in a toluene solution. From FIG. 9, it is found thatemission from PCAS in a toluene solution has a peak at 451 nm. Theemission was recognized as a bluish emission color.

A film of the obtained PCAS was formed by an evaporation method. Anionization potential of the compound in a thin film state was measuredwith a photoelectron spectrometer (manufactured by Riken Keiki Co.;Ltd., AC-2) and was found to be −5.30 eV. In addition, an absorptionspectrum of the compound in a thin film state was measured with a UV/VISspectrophotometer (manufactured by JASCO Corporation, V-550), anabsorption edge on a longer wavelength side of the absorption spectrumwas obtained from a tauc plot, and a LUMO level was measured consideringan energy of the absorption edge as a band gap (2.91 eV). The LUMO levelwas found to be −2.39 eV.

Further, a decomposition temperature T_(d) of the obtained PCAS wasmeasured with a thermo-gravimetric/differential thermal analyzer (TG/DTA320, manufactured by Seiko Instruments Inc.), and the T_(d) was found tobe 359° C. Thus, it was found that PCAS had excellent heat resistance.

An optimal molecular structure of PCAS in a ground state was calculatedwith B3LYP/6-311 (d, p) of a density functional theory (DFT). Theaccuracy of calculation of the DFT is higher than that of a Hartree-Fock(HF) method which does not consider electron correlation. In addition,the calculation cost of the DFT is lower than that of a method ofperturbation (MP) which has the same level accuracy of calculation asthe DFT. Therefore, the MT was employed in the present calculation. Thecalculation was performed using a high performance computer (HPC)(manufactured by SGI Japan, Ltd., Altix3700 DX). From this calculationresult, a HOMO level value of PCAS was obtained to be −5.00 eV.

In addition, a singlet excitation energy (band gap) of PCAS wascalculated by employing B3LYP/6-311 (d, p) of a time-dependent densityfunctional theory (TDDFT) for the molecular structure whose structurewas optimized by the DFT.: The singlet excitation energy was calculatedto be 3.04 eV.

Synthesis Example 2

Synthesis Example 2 will describe a synthetic method of4-tert-butyl-4′[N-(9-phenylcarbazol-3-yl)-N-phenylamino]stilbene(abbrev.: PCATBS) represented by the structural formula (55), as anexample of a stilbene derivative of the present invention.

[Step 1: Synthesis of 4-bromo-4′-tert-butylstilbene]

Similarly to (i) in Step 1 of Synthesis Example 1,4-bromobenzyltriphenylphosphoniumbromide was obtained. Then, 15 g (29.28mmol) of 4-bromobenzyltriphenylphosphoniumbromide and 7.12 g (43.92mmol) of 4-tert-butylbenzaldehyde were put in a 500 mL three-neckedflask. Nitrogen substitution was carried out, and 150 mL of THF wasadded and then cooled with ice. Into this, 3.94 g (35.14 mmol) ofpotassium tert-butoxide which was dissolved in 50 mL of THF was dropped,and then stirred for 24 hours at room temperature.

After the reaction, the solution was washed with water and separatedinto an organic layer and an aqueous layer. The aqueous layer wasextracted with ethyl acetate, and the extraction solution was dried withmagnesium sulfate together with the organic layer. The mixed solutionwas filtered, and the filtrate was concentrated. The obtained residuewas washed with methanol, and a precipitate in the mixed solution wascollected by suction filtration. Then, 3.30 g of a white solid which wasa target substance, was obtained in a yield of 35%.

Next, a synthesis scheme (a-2) of 4-bromo-4′-tert-butylstilbene isshown.

[Step 2: Synthesis of 3-(N-phenylamino)-9-phenylcarbazole (Abbrev.:PCA)]

3-(N-phenylamino)-9-phenylcarbazole synthesized in Step 2 of SynthesisExample 2 is the same substance as the one described in Step 2 ofSynthesis Example 1; accordingly, the description thereof is omittedhere.

[Step 3: Synthesis of4-tert-butyl-4′[N-(9-Ppenylcarbazol-3-yl)-N-phenylamino]stilbene(Abbrev.: PCATBS)]

1.0 g (3.17 mmol) of 4-bromo-4′-tert-butylstilbene, 1.06 g (3.17 mmol)of 3-(N-phenylamino)-9-phenylcarbazole (abbrev.: PCA), 0.09 g (0.159mmol) of bis(dibenzylideneacetone)palladium, and 1.52 g (15.86 mmol) ofsodium tert-butoxide were put in a 100 mL three-necked flask, andnitrogen substitution was carried out. Then, into the mixed solution, 20mL of dehydrated toluene and 0.32 g (0.159 mmol) oftri(tert-butyl)phosphine (10% hexane solution) were added and heated at80° C. for 3 hours.

After the reaction, the solution was washed with water and separatedinto an organic layer and an aqueous layer. The aqueous layer wasextracted with toluene, and the extraction solution was dried withmagnesium sulfate together with the organic layer. The mixed solutionwas filtered, and the filtrate was concentrated to obtain a residue. Theobtained residue was purified by silica gel column chromatography(toluene, hexane) and recrystallized with toluene and hexane to obtain0.67 g of a yellow solid which was a target substance in a yield of 37%.By a nuclear magnetic resonance method (¹H NMR), this compound wasascertained to be4-tert-butyl-4′-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]stilbene(abbrev.: PCATBS).

¹H NMR of this compound is shown below. In addition, FIG. 10 shows a ¹HNMR chart.

¹H NMR (300 MHz, CDCl₃); δ=8.00 (d, J=7.8 Hz, 1H), 7.94 (s, 1H),7.64-7.33 (m, 14H), 7.27-6.99 (m, 11H), 1.32 (s, 9H)

Next, a synthesis scheme (c-2) of4-tert-butyl-4′[N-(9-phenylcarbazol-3-yl)-N-phenylamino]stilbene(abbrev.: PCATBS) is shown.

FIG. 11 shows an absorption spectrum of4-tert-butyl-4′[N-(9-phenylcarbazol-3-yl)-N-phenylamino]stilbene(hereinafter referred to as PCATBS). In FIG. 11, the horizontal axisindicates a wavelength (nm) and the vertical axis indicates intensity(no unit). Note that FIG. 11 shows an absorption spectrum in a statewhere PCATBS was dissolved in a toluene solution.

FIG. 12 shows an emission spectrum of PCATBS. In FIG. 12, the horizontalaxis indicates a wavelength (nm) and the vertical axis indicatesemission intensity (arbitrary unit). FIG. 12 shows an emission spectrum(excitation wavelength: 391 nm) in a state where PCATBS was dissolved ina toluene solution. According to FIG. 12, it is found that emission fromPCATBS in a toluene solution has a peak at 445 nm. The emission wasrealized as a bluish emission color.

A film of the obtained PCATBS was formed by an evaporation method. Anionization potential of the compound in a thin film state was measuredwith a photoelectron spectrometer (manufactured by Riken Keiki Co.,Ltd., AC-2) and was found to be −5.26 eV. In addition, an absorptionspectrum of the compound in a thin film state was measured with a UV/VISspectrophotometer (manufactured by JASCO Corporation, V-550), anabsorption edge on a longer wavelength side of the absorption spectrumwas obtained from a tauc plot, and a LUMO level was measured consideringan energy of the absorption edge as a band gap (2.93 eV). The LUMO levelwas found to be −2.33 eV.

Further, a decomposition temperature T_(d) of the obtained PCATBS wasmeasured with a thermo-gravimetric/differential thermal analyzer(manufactured by Seiko Instruments Inc., TG/DTA 320), and the T_(d) wasfound to be 381° C. Thus, it was found that PCATBS had excellent heatresistance.

Synthesis Example 3

Synthesis Example 3 will describe a synthetic method of4,4′-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]stilbene (abbrev.:PCA2S) shown by the structural formula (57), as an example of a stilbenederivative of the present invention.

[Step 1: Synthesis of 4,4′-dibromostilbene]

Similarly to (i) in Step 1 of Synthesis Example 1,4-bromobenzyltriphenylphosphoniumbromide was obtained. Then, 48.05 g(93.80 mmol) of 4-bromobenzyltriphenylphosphoniumbromide and 20.83 g(112.6 mmol) of 4-bromobenzaldehyde were put in a 1 L three-neckedflask, and nitrogen substitution was carried out. 300 mL of dehydratedTHF was added into the mixed solution and cooled with ice. Into this,12.63 g (112.6 mmol) of potassium tert-butoxide which was dissolved in100 ml of THF was dropped and stirred for 24 hours at room temperature.

After the reaction, the solution was washed with water and separatedinto an organic layer and an aqueous layer. The aqueous layer wasextracted with ethyl acetate, and the extraction solution was dried withmagnesium sulfate together with the organic layer. The mixed solutionwas filtered, and the filtrate was concentrated. The obtained residuewas washed with methanol, and a precipitate in the mixed solution wascollected by suction filtration. Accordingly, 10.77 g of a white solidwhich was a target substance was obtained in a yield of 34%.

Next, a synthesis scheme (d-1) of 4,4′-dibromostilbene is shown.

[Step 2: Synthesis of 3-(N-phenylamino)-9-phenylcarbazole (Abbrev.:PCA)]

3-(N-phenylamino)-9-phenylcarbazole synthesized in Step 2 of SynthesisExample 3 is the same substance as the one described in Step 2 ofSynthesis Example 1; accordingly, the description thereof is omittedhere.

[Step 3: Synthesis of4,4′-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]stilbene (Abbrev.:PCA2S)]

1.00 g (2.95 mmol) of 4,4′-dibromostilbene, 2.19 g (6.56 mmol) of3-(N-phenylamino)-9-phenylcarbazole, 0.189 g (0.328 mmol) ofbis(dibenzylideneacetone)palladium, and 3.15 g (32.8 mmol) of sodiumtert-butoxide were put in a 100 mL three-necked flask, and nitrogensubstitution was carried out. 20 mL of dehydrated toluene and 0.66 g(0.328 mmol) of tri(tert-butyl)phosphine (10% hexane solution) wereadded thereto and heated at 80° C. for 7 hours.

After the reaction, the solution was washed with water and separatedinto an organic layer and an aqueous layer. The aqueous layer wasextracted with ethyl acetate, and the extraction solution was dried withmagnesium sulfate together with the organic layer. The mixed solutionwas filtered, and the filtrate was concentrated to obtain a residue. Theobtained residue was purified by silica gel column chromatography(toluene, hexane) and was recrystallized with chloroform and hexane;accordingly, 1.19 g of a yellow solid which was a target substance wasobtained in a yield of 47%. By a nuclear magnetic resonance method (¹HNMR), this compound was ascertained to be4,4′-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]stilbene (abbrev.:PCA2S).

¹H NMR of this compound is shown below. In addition, FIG. 13 shows a ¹HNMR chart.

¹H NMR (300 MHz, CDCl₃): δ=8.00 (d, J=7.8 Hz, 2H), 7.94 (s, 2H),7.62-7.33 (m, 20H), 7.24-6.94 (m, 10H)

Next, a synthesis scheme (e-1) of4,4′-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]stilbene (abbrev.:PCA2S) is shown.

FIG. 14 shows an absorption spectrum of4,4′-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]stilbene (hereinafterreferred to as PCA2S). In FIG. 14, the horizontal axis indicates awavelength (nm) and the vertical axis indicates intensity (no unit).Note that FIG. 14 shows an absorption spectrum in a state where PCA2Swas dissolved in a toluene solution.

FIG. 15 shows an emission spectrum of PCA2S. In FIG. 15, the horizontalaxis indicates a wavelength (nm) and the vertical axis indicatesemission intensity (arbitrary unit). FIG. 15 shows an emission spectrum(excitation wavelength: 397 nm) in a state where PCA2S was dissolved ina toluene solution. According to FIG. 15, it is found that emission fromPCA2S in a toluene solution has a peak at 446 nm. The emission wasrealized as a bluish emission color.

A film of the obtained PCA2S was formed by an evaporation method. Anionization potential of the compound in a thin film state was measuredwith a photoelectron spectrometer (manufactured by Riken Keiki Co.,Ltd., AC-2) and was found to be −5.20 eV. In addition, an absorptionspectrum of the compound in a thin film state was measured with a UV/VISspectrophotometer (manufactured by JASCO Corporation, V-550), anabsorption edge on a longer wavelength side of the absorption spectrumwas obtained from a tauc plot, and a LUMO level was measured consideringan energy of the absorption edge as a band gap (2.74 eV). The LUMO levelwas found to be −2.46 eV.

Further, a decomposition temperature T_(d) of the obtained PCA2S wasmeasured with a thereto-gravimetric/differential thermal analyzer(manufactured by Seiko Instruments Inc., TG/DTA 320), and the T_(d) wasfound to be 484° C. From this, it was found that PCA2S had excellentheat resistance.

An optimal molecular structure of PCA2S in a ground state was calculatedin a similar manner to that in Synthesis Example 1. From thiscalculation result, a HOMO level value of PCA2S was obtained to be −4.63eV.

In addition, when singlet excitation energy (band gap) of PCA2S wascalculated in a similar manner to that in Synthesis Example 1, thesinglet excitation energy was calculated to be 2.84 eV.

Synthesis Example 4

Synthesis Example 4 will describe a synthetic method of4-{N-[4-(carbazol-9-yl)phenyl]-N-phenylamino}stilbene (abbrev.: YGAS)represented by the structural formula (96), as an example of a stilbenederivative of the present invention.

[Step 1: Synthesis of 4-bromostilbene]

4-bromostilbene synthesized in Step 1 of Synthesis Example 4 is the samesubstance as the one described in Step 1 of Synthesis Example 1;accordingly, the description thereof is omitted here.

[Step 2: Synthesis of 9-[4-(N-phenylamino)phenyl]carbazole (abbrev.:YGA)]

(i) A Synthetic Method of N-(4-bromophenyl)carbazole is Described Below.

56.3 g (0.24 mol) of 1,4-dibromobenzene, 31.3 g (0.18 mol) of carbazole,4.6 g (0.024 mol) of copper iodide, 66.3 g (0.48 mol) of potassiumcarbonate, and 2.1 g (0.008 mol) of 18-crown-6-ether were put in a 300mL three-necked flask, and nitrogen substitution was carried out. 8 mLof 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone (abbrev.: DMPU)was added thereto, and stirred for 6 hours at 180° C. under a nitrogenatmosphere.

After the reaction mixture was cooled to room temperature, a precipitatewas removed by suction filtration. The filtrate was washed with dilutehydrochloric acid, saturated sodium hydrogen carbonate, and saturatedsaline in this order, and dried with magnesium sulfate. After drying,the reaction mixture was naturally filtered, and the obtained filtratewas concentrated to obtain an oily substance. The obtained oilysubstance was purified by silica gel column chromatography (hexane:ethylacetate=9:1), and was recrystallized with chloroform and hexane. Then,20.7 g of light brown plate-shaped crystal, which was a targetsubstance, was obtained in a yield of 35%. By a nuclear magneticresonance method, this compound was ascertained to beN-(4-bromophenyl)carbazole.

Next, ¹H NMR of this compound is shown.

¹H NMR (300 MHz, DMSO-d₆) δ=8.14 (d, J=7.8 Hz, 2H), 7.73 (d, J=8.7 Hz,2H), 7.46 (d, J=8.4 Hz, 2H), 7.42-7.26 (m, 6H)

(ii) Synthesis of 9-[4-(N-phenylamino)phenyl]carbazole (Abbrev.: YGA)

Next, 5.4 g (17.0 mmol) of N-(4-bromophenyl)carbazole which was obtainedin (i), 1.8 mL (20.0 mmol) of aniline, 100 mg (0.17 mmol) ofbis(dibenzylideneacetone)palladium(0) (abbrev.: Pd(dba)₂), and 3.9 g (40mmol) of sodium tert-butoxide (tert-BuONa) were put in a 200 mL,three-necked flask, and nitrogen substitution was carried out. Then, 0.1mL of 10% hexane solution of tri(tert-butyl)phosphine (abbrev.:P(tert-Bu)₃) and 50 mL of dehydrated toluene were added thereto andstirred for 6 hours at 80° C. under a nitrogen atmosphere.

The reaction mixture was filtered through florisil, celite and alumina,and the filtrate was washed with water and saturated saline, and driedwith magnesium sulfate. The reaction mixture was naturally filtered, andthe filtrate was concentrated to obtain an oily substance. The obtainedoily substance was purified by silica gel column chromatography(hexane:ethyl acetate=9:1); accordingly, 4.1 g of a target substance wasobtained in a yield of 73%. By a nuclear magnetic resonance method (¹HNMR), this compound was ascertained to be9-[4-(N-phenylamino)phenyl]carbazole (abbrev.: YGA).

Next, ¹H NMR of this compound is shown. In addition, FIGS. 16A and 16Bshow ¹H NMR charts.

¹H NMR (300 MHz, DMSO-d₆) δ=8.47 (s, 1H), 8.22 (d, J=7.8 Hz, 2H),7.44-7.16 (m, 14H), 6.92-6.87 (m, 1H)

Next, a synthesis scheme (f-1) of 9-[4-(N-phenylamino)phenyl]carbazoleis shown.

[Step 3: Synthesis of4-{N[4-(carbazol-9-yl)phenyl]-N-phenylamino}stilbene (Abbrev.: YGAS)]

0.62 g (2.38 mmol) of 4-bromostilbene, 0.88 g (2.62 mmol) of9-[4-(N-phenylamino)phenyl]carbazole, 0.068 g (0.119 mmol) ofbis(dibenzylideneacetone)palladium, and 1.14 g (11.9 mmol) of sodiumtert-butoxide were put in a 100 mL three-necked flask, and nitrogensubstitution was carried out. Then, 15 mL of dehydrated toluene and 0.24g (0.119 mmol) of tri(tert-butyl)phosphine (10% hexane solution) wereadded thereto, and stirred for 7 hours at 80° C.

After the reaction, the solution was washed with water and separatedinto an organic layer and an aqueous layer. The aqueous layer wasextracted with toluene, and the extraction solution was combined withthe organic layer and was dried with magnesium sulfate. The mixedsolution was filtered, and the filtrate was concentrated to obtain aresidue. The obtained residue was dissolved in chloroform, and thesolution was filtered through celite, florisil and alumina. The filtratewas concentrated and recrystallized with toluene and hexane.Accordingly, 1.0 g of a yellow solid, which was a target substance, wasobtained in a yield of 80%.

¹H NMR of this compound is shown below. In addition, FIG. 17 shows a ¹HNMR chart.

¹H NMR (300 MHz, CDCl₃); δ=8.14 (d, J=7.8 Hz, 2H), 7.52-7.26 (m, 19H),7.22-7.06 (m, 7H)

Next, a synthesis scheme (g-1) of4-{N-[4-(carbazol-9-yl)phenyl]-N-phenylamino}stilbene (abbrev.: YGAS) isshown.

FIG. 18 shows an absorption spectrum of4-{N[4-(carbazol-9-yl)phenyl]-N-phenylamino}stilbene (hereinafterreferred to as YGAS). In FIG. 18, the horizontal axis indicates awavelength (nm) and the vertical axis indicates intensity (no unit).Note that FIG. 18 shows an absorption spectrum in a state where YGAS wasdissolved in a toluene solution.

FIG. 19 shows an emission spectrum of YGAS. In FIG. 19, the horizontalaxis indicates a wavelength (nm) and the vertical axis indicatesemission intensity (arbitrary unit). FIG. 19 shows an emission spectrum(excitation wavelength: 382 nm) in a state where YGAS was dissolved in atoluene solution. According to FIG. 19, it is found that emission fromYGAS in a toluene solution has a peak at 428 nm. The emission wasrealized as a bluish emission color.

A film of the obtained YGAS was formed by an evaporation method. Anionization potential of the compound in a thin film state was measuredwith a photoelectron spectrometer (manufactured by Riken Keiki Co.,Ltd., AC-2) and was found to be −5.65 eV. In addition, an absorptionspectrum of the compound in a thin film state was measured with a UV/VISspectrophotometer (manufactured by JASCO Corporation, V-550), anabsorption edge on a longer wavelength side of the absorption spectrumwas obtained from a tauc plot, and a LUMO level was measured consideringan energy of the absorption edge as a band gap (2.99 eV). The LUMO levelwas found to be −2.66 eV.

Further, a decomposition temperature T_(d) of the obtained YGAS wasmeasured with a thermo-gravimetric/differential thermal analyzer(manufactured by Seiko Instruments Inc., TG/DTA 320), and the T_(d) wasfound to be 384° C. Thus, it was found that YGAS had excellent heatresistance.

An optimal molecular structure of YGAS in a ground state was calculatedin a similar manner to that in Synthesis Example 1. From thiscalculation result, a HOMO level value of YGAS was obtained to be −5.10eV.

In addition, when a singlet excitation energy (band gap) of YGAS wascalculated in a similar manner to that in Synthesis Example 1, thesinglet excitation energy was calculated to be 3.09 eV.

Synthesis Example 5

Synthesis Example 5 will describe a synthetic method of4,4′-bis{N-[4-(carbazol-9-yl)phenyl]-N-phenylamino}stilbene (abbrev.:YGA2S) represented by the structural formula (129), as an example of astilbene derivative of the present invention.

[Step 1: Synthesis of 4,4′-dibromostilbene]

4,4′-dibromostilbene synthesized in Step 1 of this Synthesis Example 5is the same substance as the one described in Step 1 of SynthesisExample 3; accordingly, the description thereof is omitted here.

[Step 2: Synthesis of 9-[4-(N-phenylamino)phenyl]carbazole (Abbrev.:YGA)]

9-[4-(N-phenylamino)phenyl]carbazole synthesized in Step 2 of thisSynthesis Example 5 is the same substance as the one described in Step 2of Synthesis Example 4; accordingly, the description thereof is omittedhere.

[Step 3: Synthesis of4,4′-bis{N-[4-(carbazol-9-yl)phenyl]-N-phenylamino}stilbene (Abbrev.:YGA2S)]

1.00 g (2.95 mmol) of 4,4′-dibromostilbene, 2.19 g (6.56 mmol) of9-[4-(N-phenylamino)phenyl]carbazole, 0.189 g (0.328 mmol) ofbis(dibenzylideneacetone)palladium, and 3.15 g (32.8 mmol) of sodiumtert-butoxide were put in a 100 mL three-necked flask, and nitrogensubstitution was carried out. Then, 20 mL of dehydrated toluene and 0.66g (0.328 mmol) of tri(tert-butyl)phosphine (10% hexane solution) wereadded thereto and heated at 80° C. for 7 hours.

After the reaction, the solution was washed with water and was separatedinto an organic layer and an aqueous layer. Then a precipitate in themixed solution was collected by suction filtration. The filtrate wasdissolved in chloroform and the solution was filtered through celite,florisil and alumina. The filtrate was concentrated and recrystallizedwith chloroform and hexane. Accordingly, 1.51 g of a yellow solid whichwas a target substance was obtained in a yield of 60%.

¹H NMR of this compound is described below. In addition, FIG. 20 is a ¹HNMR chart.

¹H NMR (300 MHz, CDCl₃); δ=8.14 (d, J=7.8 Hz, 4H), 7.47-7.28 (m, 28H),7.25-7.08 (m, 10H), 7.02 (s, 2H)

Next, a synthesis scheme (h-1) of4,4′-bis{N[4-(carbazol-9-yl)phenyl]-N-phenylamino}stilbene (abbrev.:YGA2S) is shown.

FIG. 21 shows an absorption spectrum of4,4′-bis{N[4-(carbazol-9-yl)phenyl]-N-phenylamino}stilbene (hereinafterreferred to as YGA2S). In FIG. 21, the horizontal axis indicates awavelength (nm) and the vertical axis indicates intensity (no unit).Note that FIG. 21 shows an absorption spectrum in a state where YGA2Swas dissolved in a toluene solution.

FIG. 22 shows an emission spectrum of YGA2S. In FIG. 22, the horizontalaxis indicates a wavelength (nm) and the vertical axis indicatesemission intensity (arbitrary unit). FIG. 22 shows an emission spectrum(excitation wavelength: 395 nm) in a state where YGA2S was dissolved ina toluene solution. From FIG. 22, it is found that emission from YGA2Sin a toluene solution has a peak at 435 nm. The emission was realized asa bluish emission color.

A film of the obtained YGA2S was formed by an evaporation method. Anionization potential of the compound in a thin film state was measuredwith a photoelectron spectrometer (manufactured by Riken Keiki Co.,Ltd., AC-2) and was found to be −5.77 eV. In addition, an absorptionspectrum of the compound in a thin film state was measured with a UV/VISspectrophotometer (manufactured by JASCO Corporation, V-550), anabsorption edge on a longer wavelength side of the absorption spectrumwas obtained from a tauc plot, and a LUMO level was measured consideringan energy of the absorption edge as a band gap (2.81 eV). The LUMO levelwas found to be −2.96 eV.

Further, a decomposition temperature T_(d) of the obtained YGA2S wasmeasured with a thermo-gravimetric/differential thermal analyzer(manufactured by Seiko Instruments Inc., TG/DTA 320), and the T_(d) wasfound to be 483° C. Thus, it was found that YGA2S had excellent heatresistance.

An optimal molecular structure of YGA2S in a ground state was calculatedin a similar manner to that in Synthesis Example 1. From thiscalculation result, a HOMO level value of YGA2S was obtained to be −5.20eV.

In addition, when singlet excitation energy (band gap) of YGA2S wascalculated in a similar manner to that in Synthesis Example 1, thesinglet excitation energy was calculated to be 2.87 eV.

Example 2

Example 2 will describe a case where a light-emitting element ismanufactured using a stilbene derivative of the present invention in apart of a layer including a luminescent substance. Specifically, alight-emitting element which is manufactured using a stilbene derivativeof the present invention as a guest material of a light-emitting layerof a layer including a luminescent substance, is described.

First, a first electrode of a light-emitting element was formed over asubstrate. In this example, ITSO (indium tin oxide containing siliconoxide obtained by a sputtering method by using a target which is ITOcontaining 2 to 10 wt % of silicon oxide), which was a transparentconductive film, was used for the first electrode. ITO was formed with athickness of 110 nm by a sputtering method, and etched such that thefirst electrode had a shape of 2 mm×2 mm.

Next, as a pretreatment for forming the light-emitting element over thefirst electrode, a surface of the substrate was washed with a porousresin (typically formed of PVA (polyvinyl alcohol), nylon or the like),and a heat treatment was then conducted at 200° C. for 1 hour underatmosphere air. Then, a UV ozone treatment was conducted for 370seconds, and a heat treatment was further conducted at 170° C. for 30minutes under reduced pressure.

Next, a layer including a luminescent substance was formed over thefirst electrode. Note that the layer including a luminescent substancein this example was formed by sequentially stacking a hole injectinglayer, a hole transporting layer, a light-emitting layer, an electrontransporting layer, and an electron injecting layer by a vacuumevaporation method.

First, the hole injecting layer was formed at 50 nm by coevaporationsuch that a mass ratio of4,4′-bis(N-{4-[N,N-bis(3-methylphenyl)amino]phenyl}-N-phenylamino)biphenyl(abbrev.: DNTPD) to molybdenum oxide became 4:2. The hole transportinglayer was formed at 10 nm by evaporating NPB.

Next, the light-emitting layer was formed. The thickness thereof was 30nm. The structure of the light-emitting layer will be described later.

Further, the electron transporting layer was formed at 10 nm byevaporating bathocuproin (abbrev.: BCP). The electron injecting layerwas formed at 20 nm by coevaporation such that a mass ratio of Alq₃ tolithium became 1:0.01.

Then, Al was formed at 200 nm by vacuum evaporation, as a secondelectrode; accordingly, the element was completed. Sealing was conductedby using a sealing substrate under a nitrogen atmosphere, so as not toexpose the element formed over the substrate to atmosphere.

Here, the following elements were examined: Element 1 is an elementincluding, as the light-emitting layer in the above-described structure,a layer which was formed by coevaporation such that a mass ratio of4,4′-di(N-carbazolyl)biphenyl (abbrev.: CBP) to PCAS, a stilbenederivative of the present invention, became 1:0.1; Element 2 is anelement including, as the light-emitting layer in the above-describedstructure, a layer which was formed by coevaporation such that a massratio of CBP to PCATBS, a stilbene derivative of the present invention,became 1:0.1; Element 3 is an element including, as the light-emittinglayer in the above-described structure, a layer which was formed bycoevaporation such that a mass ratio of CBP to PCA2S, a stilbenederivative of the present invention, became 1:0.1; Element 4 is anelement including, as the light-emitting layer in the above-describedstructure, a layer which was formed by coevaporation such that a massratio of CBP to YGAS, a stilbene derivative of the present invention,became 1:0.05; and Element 5 is an element including, as thelight-emitting layer in the above-described structure, a layer which wasformed by coevaporation such that a mass ratio of CBP to YGA2S, astilbene derivative of the present invention, became 1:0.05.

The light-emitting elements manufactured in the above-described manner(elements 1 to 5) were applied with a voltage so as to be driven, andcharacteristics of the elements were measured.

FIG. 23 shows luminance-current density characteristics of the element1, FIG. 24 shows luminance-voltage characteristics of the element 1,FIG. 25 shows current efficiency-luminance characteristics of theelement 1, and FIG. 26 shows an emission spectrum of the element 1. Whenthe element 1 was applied with a voltage of 7.4 V, the current densitywas 50.9 mA/cm², the luminance was 972 cd/cm², and the currentefficiency was 1.91 cd/A. In addition, the element 1 had a peak at 448nm, and CIE chromaticity coordinates were (x, y)=(0.15, 0.13), which wasan excellent color purity, and the element 1 exhibited blue lightemission.

FIG. 27 shows luminance-current density characteristics of the element2, FIG. 28 shows luminance-voltage characteristics of the element 2,FIG. 29 shows current efficiency-luminance characteristics of theelement 2, and FIG. 30 shows an emission spectrum of the element 2. Whenthe element 2 was applied with a voltage of 7.0 V, the current densitywas 58.7 mA/cm², the luminance was 957 cd/cm², and the currentefficiency was 1.63 cd/A. In addition, the element 2 had a peak at 442nm, and CIE chromaticity coordinates were (x, y)=(0.15, 0.10), which wasan excellent color purity, and the element 2 exhibited blue lightemission.

FIG. 31 shows luminance-current density characteristics of the element3, FIG. 32 shows luminance-voltage characteristics of the element 3,FIG. 33 shows current efficiency-luminance characteristics of theelement 3, and FIG. 34 shows an emission spectrum of the element 3. Whenthe element 3 was applied with a voltage of 8.4 V, the current densitywas 34.9 mA/cm², the luminance was 1100 cd/cm², and the currentefficiency was 3.16 cd/A. In addition, the element 3 had a peak at 458nm, and CIE chromaticity coordinates were (x, y)=(0.16, 0.20), and theelement 3 exhibited blue light emission.

FIG. 35 shows luminance-current density characteristics of the element4, FIG. 36 shows luminance-voltage characteristics of the element 4,FIG. 37 shows current efficiency-luminance characteristics of theelement 4, and FIG. 38 shows an emission spectrum of the element 4. Whenthe element 4 was applied with a voltage of 12.2 V, the current densitywas 180 mA/cm², the luminance was 941 cd/cm², and the current efficiencywas 0522 cd/A. In addition, the element 4 had a peak at 436 nm, and CIEchromaticity coordinates were (x, y)=(0.15, 0.07), which was anexcellent color purity, and the element 2 exhibited deep blue lightemission.

FIG. 39 shows luminance-current density characteristics of the element5, FIG. 40 shows luminance-voltage characteristics of the element 5,FIG. 41 shows current efficiency-luminance characteristics of theelement 5, and FIG. 42 shows an emission spectrum of the element 5. Whenthe element 5 was applied with a voltage of 10.8 V, the current densitywas 39.4 mA/cm², the luminance was 922 cd/cm², and the currentefficiency was 2.34 cd/A. In addition, the element 5 had a peak at 443nm, and CIE chromaticity coordinates were (x, y)=(0.15, 0.11), which wasa favorable color purity, and the element 5 exhibited blue lightemission.

In this example, an element was formed as Element 6, in which CzPA wasused instead of CBP in the light-emitting layer of Element 5 describeabove, and coevaporation was conducted such that a mass ratio of CzPA toYGA2S became 1:0.05 and in which Alq₃ was used instead of BCP for theelectron transporting layer. Further, an element formed in a similarmanner as the element 6 except that the hole injecting layer was formedat 50 nm by coevaporation such that a mass ratio of NPB to molybdenumoxide became 4:1 was manufactured as Element 7. Element characteristicsthereof were measured similarly.

FIG. 43 shows luminance-current density characteristics of the element6, FIG. 44 shows luminance-voltage characteristics of the element 6,FIG. 45 shows current efficiency-luminance characteristics of theelement 6, and FIG. 46 shows an emission spectrum of the element 6. Whenthe element 6 was applied with a voltage of 6.2 V, the current densitywas 16.1 mA/cm², the luminance was 1040 cd/cm², and the currentefficiency was 6.42 cd/A. In addition, the element 6 had a peak at 444nm, and CIE chromaticity coordinates were (x, y)=(0.17, 0.18), which wasan excellent color purity, and the element 6 exhibited blue lightemission. From this result, it can be realized that the element 6 hashigher efficiency than the above-described elements 1 to 5.

FIG. 47 shows luminance-current density characteristics of the element7, FIG. 48 shows luminance-voltage characteristics of the element 7,FIG. 49 shows current efficiency-luminance characteristics of theelement 7, and FIG. 50 shows an emission spectrum of the element 7. Whenthe element 7 was applied with a voltage of 6.4 V, the current densitywas 37.3 mA/cm², the luminance was 1090 cd/cm², and the currentefficiency was 2.93 cd/A. In addition, the element 7 had a peak at 444nm, and CIE chromaticity coordinates were (x, y)=(0.16, 0.17), which wasan excellent color purity, and the element 7 exhibited blue lightemission.

An initial luminance of the element 7 was set at 500 cd/m², and theelement 7 was driven under a condition of constant current density.After a lapse of 200 hours, the element 7 had 86% (relative luminance)of the initial luminance (500 cd/m²).

Further, the above-described test was continued and the result as shownin FIG. 51 was obtained. In FIG. 51, the horizontal axis indicates adriving time (h), and the vertical axis indicates a relative luminance(%) w hen 500 cd/m² of the luminance was considered as 100%. Accordingto FIG. 51, the predicted half-life period of the luminance, in the casewhere the initial luminance was 500 cd/m², was 2800 hours. Accordingly,it can be said that the element 7 has an excellent long life.

This application is based on Japanese Patent Application serial Nos.2005-292366 filed in Japan Patent Office on Oct. 5, 2005, and2005-343674 filed in Japan Patent Office on Nov. 29, 2005, the entirecontents of which are hereby incorporated by references.

Explanation of Reference

101: first electrode, 102: second electrode, 103: layer including aluminescent substance, 104: light-emitting layer, 201: substrate, 202 a:source region, 202 b: drain region. 203: channel forming region, 204:gate insulating film, 205: gate electrode, 206: interlayer insulatingfilm, 207 a: source electrode, 207 b: drain electrode, 208: TFT, 209:first electrode, 210: insulator, 301: substrate, 302: gate electrode,303: gate insulating film, 304: channel forming region, 305 a: sourceregion, 305 b: drain region, 306 a: source electrode, 306 b: drainelectrode, 307: interlayer insulating film, 308: TFT, 309: firstelectrode, 310: insulator, 321: substrate, 322: gate electrode, 323:gate insulating film, 324: channel forming region, 325 a: source region,325 b; drain region, 326 a: source electrode, 326 b: drain electrode,327: interlayer insulating film, 328: TFT, 329: first electrode, 330:insulator, 331: protective layer, 401: driver circuit portion (sourcedriver circuit), 402: pixel portion, 403: driver circuit portion (gatedriver circuit), 404: sealing substrate, 405: sealant, 407: space, 408:wire, 409: FPC (flexible printed circuit), 410: element substrate, 411:switching TFT, 412: current control TFT, 413: first electrode, 414:insulator, 416: layer including a luminescent substance, 417: secondelectrode, 418: light-emitting element, 423: n-channel TFT, 424:p-channel TFT 8001: main body, 8002: display portion, 8101: main body,8102: display portion, 8201: main body, 8202: display portion, 8301:main body, 8302: display portion, 8401: main body, and 8402: displayportion.

1. A light-emitting device comprising: a first electrode over asubstrate; a second electrode over the first electrode; and a layerbetween the first electrode and the second electrode, the layerincluding a stilbene derivative represented by a general formula (1),

wherein R¹ is hydrogen, an alkyl group having 1 to 4 carbon atoms, or anaryl group having 6 to 25 carbon atoms; wherein R² is an alkyl grouphaving 1 to 4 carbon atoms or an aryl group having 6 to 25 carbon atoms;wherein each of R³ to R⁵ is hydrogen or an alkyl group having 1 to 4carbon atoms; and wherein Ar¹ is an aryl group having 6 to 25 carbonatoms.
 2. The light-emitting device according to claim 1, wherein thelayer including a stilbene derivative represented by a general formula(2),

wherein R¹ is hydrogen, an alkyl group having 1 to 4 carbon atoms, or anaryl group having 6 to 25 carbon atoms; wherein R² is an alkyl grouphaving 1 to 4 carbon atoms or an aryl group having 6 to 25 carbon atoms;wherein each of R³ to R⁵ is hydrogen or an alkyl group having 1 to 4carbon atoms; and wherein each of R⁶ to R¹⁰ is hydrogen, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms.
 3. A light-emitting device comprising: a first electrode over asubstrate; a second electrode over the first electrode; and a layerbetween the first electrode and the second electrode, the layerincluding a stilbene derivative represented by a general formula (3),

wherein R¹ is hydrogen, an alkyl group having 1 to 4 carbon atoms, or anaryl group having 6 to 25 carbon atoms; wherein R² is an alkyl grouphaving 1 to 4 carbon atoms or an aryl group having 6 to 25 carbon atoms;and wherein Ar¹ is an aryl group having 6 to 25 carbon atoms.
 4. Thelight-emitting device according to claim 3, wherein the layer includinga stilbene derivative represented by a general formula (4),

wherein R¹ is hydrogen, an alkyl group having 1 to 4 carbon atoms, or anaryl group having 6 to 25 carbon atoms; wherein R² is an alkyl grouphaving 1 to 4 carbon atoms or an aryl group having 6 to 25 carbon atoms;and wherein each of R⁶ to R¹⁰ is hydrogen, an alkyl group having 1 to 4carbon atoms, or an aryl group having 6 to 25 carbon atoms.
 5. Alight-emitting device comprising: a first electrode over a substrate; asecond electrode over the first electrode; and a layer between the firstelectrode and the second electrode, the layer including a stilbenederivative represented by a general formula (5),

wherein each of R¹ and R² is hydrogen, an alkyl group having 1 to 4carbon atoms, or an aryl group having 6 to 25 carbon atoms; wherein eachof R³ to R⁵ is hydrogen or an alkyl group having 1 to 4 carbon atoms;and wherein Ar¹ is an aryl group having 6 to 25 carbon atoms.
 6. Thelight-emitting device according to claim 5, wherein the layer includinga stilbene derivative represented by a general formula (6),

wherein each of R¹ and R² is hydrogen, an alkyl group having 1 to 4carbon atoms, or an aryl group having 6 to 25 carbon atoms; wherein eachof R³ to R⁵ is hydrogen or an alkyl group having 1 to 4 carbon atoms;and wherein each of R⁶ to R¹⁰ is hydrogen, an alkyl group having 1 to 4carbon atoms, or an aryl group having 6 to 25 carbon atoms.
 7. Alight-emitting device comprising: a first electrode over a substrate; asecond electrode over the first electrode; and a layer between the firstelectrode and the second electrode, the layer including a stilbenederivative represented by a general formula (7),

wherein each of R¹ and R² is hydrogen, an alkyl group having 1 to 4carbon atoms, or an aryl group having 6 to 25 carbon atoms; and whereinAr¹ is an aryl group having 6 to 25 carbon atoms.
 8. The light-emittingdevice according to claim 7, wherein the layer including a stilbenederivative represented by a general formula (8),

wherein each of R¹ and R² is hydrogen, an alkyl group having 1 to 4carbon atoms, or an aryl group having 6 to 25 carbon atoms; and whereineach of R⁶ to R¹⁰ is hydrogen, an alkyl group having 1 to 4 carbonatoms, or an aryl group having 6 to 25 carbon atoms.
 9. Thelight-emitting device according to claim 1, wherein the substrate ismade of transparent plastic.
 10. The light-emitting device according toclaim 1, wherein the light-emitting device is a lighting or alight-source of a traffic signal machine.
 11. The light-emitting deviceaccording to claim 3, wherein the substrate is made of transparentplastic.
 12. The light-emitting device according to claim 3, wherein thelight-emitting device is a lighting or a light-source of a trafficsignal machine.
 13. The light-emitting device according to claim 5,wherein the substrate is made of transparent plastic.
 14. Thelight-emitting device according to claim 5, wherein the light-emittingdevice is a lighting or a light-source of a traffic signal machine. 15.The light-emitting device according to claim 7, wherein the substrate ismade of transparent plastic.
 16. The light-emitting device according toclaim 7, wherein the light-emitting device is a lighting or alight-source of a traffic signal machine.